I'm glad to hear that the experimental version worked without crashing! It seems there might be some compatibility issues with the stable 1.31d version and your save game. Try these steps:
Back Up Save: Before proceeding, backup your save game files in case anything goes wrong.
Verify Files: Use GOG's or the game's built-in tools to verify the integrity of the game files. This might fix any corrupted data causing crashes.
Community Support: Check online forums or the game's community hub for solutions. Others might have faced similar issues and found workarounds.
Rollback to Experimental: If your save game works well on the experimental version, consider rolling back to it until the stable version stabilizes or a patch is released.
Contact Support: If the issue persists, contact the game's support. They might be aware of the issue and could provide guidance or a timeline for a fix.
Remember, technical issues like crashes can sometimes be complex, and a little patience might be needed. Good luck!