I cant really help you, I play KSP for 4 days now after 2 years without playing it I dont know much about everything. As Singing Boyo said, kopernicus made an alert by telling us "DON'T LOAD YOUR SAVE" and to read the log file.
I tried to load a sandbox game but the game was completly broken at this point : it was stuck at "loading" forever. For what I understand in the log file, if you remove the Pol terrain, it should fix it.
Btw, thank you for this mod, the game looks awesome now.