I was a bit curious about this issue of failed GUI in the mountain caves, so I checked it out on my computer. I have the windows 64 version 0.5.25 from itch.io(it's free to download there BTW). I reached the caves on day 1 without completing any core quests in story mode and had no issues there. So I have doubts that progressing the story will fix your problem, though I am still uncertain as to the cause of the problem.
The game should start with 2 windows for most OS: the game window and a console window. I would recommend putting the console where you can see the left side so you can see when the errors appear, and traveling to the mountain caves simply to trigger it. If there are many errors, then the first is generally the most relevant, but it can help to see the rest.
As a side note, the races issue for mountain caves was fixed for 0.5.25 as guards no longer use the regions as the random pool. So changing that entry by itself will have no impact on the game, as none of the encounters there use the regional race pool. "oosesgroup" and "solospider" are monsters, "treasurechest" has no enemies, and "goblingroup" is only goblins.