It seems to be a save file related issue. I had saves from 4 different runs at various stages, and the problem seems to affect only runs that were STARTED after the patch 4 was applied. Older save files work perfectly. I suspect this is linked to some new attempt at performance/size optimization. Older save files probably contain some information that is missing from the new ones, so the game tries (VERY slowly) to load these when needed. The fact that there was a hotfix released a few days ago without solving this major bug is not the best sign. It could happen that these new save files are irrevocably corrupted. In any case I had to put my recent run on hold, because it is unplayable.
