I believe the issue is how big the game is
HO THANK YOU !
I suspect one or 2 Things ...
1 = the Voxels Size Exceded the limits ...
Thing that we canot fix without Destroing Parts of the Map ... on all 5 terrains ...
... Wich is something that will take us .. like 4 days for Rebuilding it ...
2 = Goes way beyond the Playable Boundaries ... And might be Causing precision issues ...
.. But we dont really know Were the Level boundaries are beside ... Fiting it on the Sky Box Size ...
3 = Terrain Folliage ... instances Count ... We Tryed to Optimizing it Still fiting our Art direction ...
Its on our Game design to use the Foliage colision sistem on the biggest foliage cristals and trees , as stop and launch platforms wille the player is flying ...
But foliage collision system is buggy just works partially ( players flying stop and colide and try to land on it ... But then just pass trough )
Also each foliage item with collision makes huge frame rate drops overhead ... So we were forced to remove collision option on all folliage models ... And that totally breacks the desired gameplay experience ...
There are alot issues with folliage not working, optimizing lods , fading spawning, angle slope spawning , that in min or max settings do nothing, and overkill performance , that there is not on default unreal Engine ... And we suppose the fault is on the voxelplugin.com that Core engine uses, that beside beying a older not updated on latest features version ... Also breaks the Foliage Sistem Features ...
Wich is normal because is a external single developer that made the voxel plugin , not supported by epic ... And its in very early stage development , comparing to 15 years old Mature Solutions as Voxelfarm.com , that has full sdk conection to Unreal, and was batletested many years At Electronic Arts, Everquest Next Voxel Mmo Game ...
I really Sugest Manticore to Add Voxelfarm to CORE as soon possible ... As secoundary / primary option for terrains ... And as Third Option Mantain the Vanilla Unreal World composition terrains ... That are fully suported with a unlimited world composition grid of terrains up to continental levels if needed ... Also because water and foliage as well dynamic procedural splines and folliage are highly upgraded with extraordinary new and performant features, roled out in Unreal Latests ...
Was really bad choice to remove / not use default Unreal composition world grid streaming terrain tools of unreal ... Because of performance and Array of features ...
And if need high candy unlimited planetary level voxel worlds features ... Voxel farm is the very best ... Also because has a external voxels editor, so it easy ups the full features integration with Unreal ...
Unleashing users creations levels compositions to be able to create whole worlds if needed, with cut edge tecnology that can even stream on cloud servers in realtime even in browsers ... So its really something else ... CORE really needs ...
We were part of the beta testing of voxel farm as customers since 10 years ago ... And their Unreal / Unity Integration ... is really unbelievable ...
You Guys at Manticore should give a look and contact Miguel Cepero, the main dev at VoxelFarm.com
https://twitter.com/voxelfarm
https://twitter.com/miguelcepero
Anyway ...
We tried to Test stress CORE to its Limits here ...
And Actually Works Enouph good and Still Playable on CLIENT Side ... So why not the SERVER Side dont Acept it ? Its not configured to the Amount of information being passed trough ?
Or is Creating unecessary Garbage / Temp / Undos / Client side Files ... Then is trying to Upload Full Project + Garbage ... To Server ? ...
And if that is ... Shouldnt CORE Have a CLEANING PROJECT Files Tool ? ... In order to Backup & Remove from Project all every files ... Imported in the Project ... Not used on the Level Scene ...
I think that is the core of the main problem happening in this massive world project here ...
( UNREAL Engine has a very cool "Export Selected assets / Groups / folders with all dependencies" As well Migrate Scene With all Dependencies to Another project Features ... That would be so Awsome to Be added to core , to help clean up Projects Levels Before Submiting to Server ... )
As there are no concept of "multiple Levels " in one project .. like there is in Unreal engine ... And no migration tools ...
So what is being uploaded to Manticore Servers .. is "the whole project" Even with things not used in the scene .. and Extra Temp datas Etc ...
Im sure that can cause a big overhead ...
As we always marked each changed assets with Development version Names ...
We did try to do some tests and deleting All unessesary not used Assets and temp data and all we we could ( just to test the diference )
And the whole Project come down from 1gb to 300mb ...
Now if its the 1GB "Whole project folder" Core is trying to send to the server ...
Well ...
GLADLY CORE Project structure ... are just REFERENCES to Existing Provided data files ...
Usually our UNREAL projects that go near this level of detail ... they take literary 10Gb Disck space ...
With CORE its just 1 GB Each project like ...
But still too much to upload to a Server to Process ....
WHY the Project CLEANING / MIGRATION / Export Selected with dependencies ...
TOOLS in CORE are so needed for next versions ....
Because its just so hard for us to Keep things Tidy and Specially DEBUG if problems like this and others arrive ...
At this Point is better for us to do a Whole new project ...
As seams this one is BROKEN without Repairing ...
It reached a Point that we tried to Just Make a Level with Sky and player ...
Delete all everything ... And takes along time uploading ... and at the end still gives same Errors Not be able publish game ...
( that is the Prove that CORE is uploading the Whole project folder with all non used files and temp garbage ...
NOT just the level and Dependencies Only as it Should ... )
After 1 whole day trying ...
That is the main major problem we see we are facing ...
I think ... Instead of Trying to Clean up ...
We Should Start on a BLANK Project then adding all back Part by part
And Test publishing Privately many Times till we Get What is Making the Error more Exactly ...
But = there is no Way to make a TERRAIN as a Template ... And Migrate a terrain + Instances to another project ...
So if this is Buged ... We have to Start All Again ?
But its at least 150+ hours of work .. Gone ...
Ho noo...
OK so i will try to hack it ...
I noticed that we can "copy the terrain files" to new projects by ...
1 = make new terrain in blank project .. Close project
2 = copy the old .terrains FILES from another project .. rename to the same name in project folder ... Overight ...
It will Load the terrain in new Blank project with Old Voxel data ...
We still have the Not be able to migrate the instances ...
But we will copy the Settings 1 by 1 ...
I will try to Do This the next Hours and UpDate The Submission ...
And we will keep you updated on improvments !
ANYWAY ! Greath CASE STUDY / Debug Situation for Core Developers to Expand Core Limits ...
AND PLEASE ! Dear CORE developers !
Insert http://VOXELFARM.com Terrains in CORE !
It has a Unreal Plugin ... and its the greatest
We so much need that !
THANK YOU SO MUCH !
FOR THE AWSOME FAST SUPPORT !
Thank you for your Time.
And thanks so much for listening !
__
Ruben ismael
SOULSSHINE@GMAIL.COM
THE SOULSSHINE Studio
http://Artstation.com/SOULSSHINE
http://Deviantart.com/SOULSSHINE
http://Facebook.com/SOULSSHINESTudios 
Dearest BUCK ...
It Seams its not THE TERRAINS error ...
We tryed to Publish the Level even Without Terrains at All ...
But is Still giving Failed to Create Game Error ...
CAN YOU PLEASE TRY TO PUBLISH The game From there to your Account ?
We will keep trying but ...
Maybe is something on our End ...
As seams we canot publish Any Game AT ALL from here ...
As Always Says INVALID REQUEST ... ( Full Game HashField is Required )
It Looks like the Project takes Too long to Upload ...
Then reaches a Point the Server Dont Recognize the Game Parameters
So it Trows Alot Invalid request Errors of ClientHash / FullGamehash / GameHostHash ...
Even without terrains ... or Big Level at all ...
YoU Work at Manticore right ?
WHAT YOU THINK IS HAPPENING ?
Can you please Try to Publish the Game there .
Is There someone / mail / Place ... we Should Contact About this ( Invalid Request ) Errors ...
THANKS SO MUCH For your Support !
THANK YOU SO MUCH ! For your time .
__
Ruben ismael
SOULSSHINE@GMAIL.COM
THE SOULSSHINE Studio
http://Artstation.com/SOULSSHINE
http://Deviantart.com/SOULSSHINE
http://Facebook.com/SOULSSHINESTudios 
WELL ... We Dont Know What to do Anymore
We tried for 4 hours all possible Ways ...
And ... Even Just The project EMPTY All deleted in scene and Just the Skybox
Still takes Alot Time Uploading to Manticore Servers
And in the end Trows the Same ERROR ...
( Invalid Request , full Hashfield is required )
Uff ...