A pawn with a title in colony was dying from bleeding and the title inheritance event fired but pawn next in line was in a caravan and didn't get the title. Dying pawn's death counter was stuck at 0 seconds. Inheritance event keept firing in an exponential rate and slowed down the game. Pawn with a title was a yeoman and other was without any title.
Create two pawns one with a title and the other as next in line. Send the next in line with a caravan on route and kill the pawn with the title by bleeding.
Save file is too large even after compression. I can't send an attachment. Here's a google drive link if you want:
https://drive.google.com/file/d/1Al7bpDWJCXXLtMoXXC_LpRwNCZfa4M_U/view?usp=sharing
This also happens if the the inheriting pawn has just been kidnapped during the same raid that killed the titled colonist.