Hello again MythAtelier Team,
Congratulations on the 1.2 release! Happy to say I downloaded to ASAP as soon as I saw it released today. The new features seem great by the way and I can't wait to get them into my current game.
I *THINK* I may have found part of the issue after more testing with your demo and my own game. As far as I can tell (and I preface this by saying upfront I know next to nothing about Javascript, coding, etc) - the Text Codes commonly used via 'YEP Message Core' are what is causing the errors found above and persisting into the 1.2 release.
I've included some screenshots but here is what I was able to find using the 1.2 Demo Project that I loaded with YEP_Core, YEP Message Core, and YEP_Skill Core plugins. In 'Test 1' I included the YEP Text Code of \I[170] to show the 170th icon in my icon set in the skill description text. When launching the game and initiating the battle, I encountered the below error.
In 'Test 2' where I kept all the same YEP plugins but REMOVED the Text Code from the skill description text. When launching the game and initiating the battle, the game worked normally without any issues whatsoever. This would suggest that the Text Codes from YEP Message Core (\V[n], \N[n], \P[n], \G, \I[n], etc) are what is causing the errors.
Again, I am really appreciative for the work that went into the latest release for 1.2 and your Trello Board has me very excited for the future of this plugin. I hope this feedback is of some use, as I am sure there will be many people like myself who would love this to play nice with the usual Yanfly plugin collection that the majority of RPGMaker users tend to use.