check the console error log, first and foremost.
expansionfarms.gd may be having a bad day.
It looks like Constants broke the game (the very top error). I would recommend disabling Constants and trying again. I can't promise they are compatible.
Edit: The snailsbreeding issue is one that is fixed via the hotfix that I posted in the main post. Deactivate Aric's, drop that into your mansion file in appdata/strive/mods/arics/scripts, and reactivate Aric's. That should clear up the snailsbreeding issue until v0.9.5 is released.
The Constant's error should be resolved via the following - https://itch.io/post/1488530
The constants mod is working fine, it is quite robust and is unlikely to effect the rest of the game. The message is simply a harmless notification that it didn't like the value of a variable. There is a small oversight in the mod system's RegEx, and a variable in variables.gd that has a syntax that has incompatible with the mod system. The rest of the errors are the result of problems solely related to Arics Expansion.
Huh, looks like multiple problems can cause this same symptom, heh. In my case the error message is:
SCRIPT ERROR: farminspect: Invalid get index 'stallbedding' (on base: 'Dictionary').
At: res://files/scripts/Mansion.gd:3651
In fact, all the farm panel buttons are throwing a similar error:
SCRIPT ERROR: _on_vatsbutton_pressed: Invalid get index 'bottler' (on base: 'Dictionary').
At: res://files/scripts/Mansion.gd:5575
SCRIPT ERROR: _on_workersbutton_pressed: Invalid get index 'farmhand' (on base: 'Dictionary').
At: res://files/scripts/Mansion.gd:5846
SCRIPT ERROR: _on_storebutton_pressed: Invalid get index 'containers' (on base: 'Dictionary').
At: res://files/scripts/Mansion.gd:5902
Any errors above this one? Stallbedding or any of the farm panel buttons don't usually through up errors unless it's misinstalled. There is a file as a hotfix in the main post for Mansion.gd that should clear up the issue if it's related to the snailsbreeding node (if that's part of any error code above that one)
Was this a new or existing save? And any other mods installed? Finally, have you reinstalled the mod and/or double checked the install steps or video? That includes deleting the backups folder, as it looks like your Mansion.gd is acting like the farm’s variables aren’t a thing (ie: vanilla code) in your globals & farm file.
Might have the solution for you in my recent comments. Fixed it for myself and one other person. On old saves you don't have all of the code you need so you need it added. Follow the post where I said "Okay well this was miserable" first and then after that do what is in the "Buckle up buttercups" post.
Thanks for the reply, although your edit made me feel kind of dumb. I had found the fix in a previous post before mine (the line of code being "snailsbreeding" instead of "snailbreeding"), but when I made the changes myself it still wouldn't work and I couldn't figure out why. I completely forgot that I had to deactivate and reactivate Aric's if I expected the changes in code to be recognized by the game and not throw those errors.