Facing the same issue and was not able to fix it yet. I also have mods and tried to disable them but did not help.
When checking the callbacks stack, I did notice that the issue was related to the hero heal event, so I tried using the console to heal the whole party, hoping it would prevent the code executing, but it did not help.
Lastly, I did notice that it might be location based or some NPC on the map, because on one save, I moved from the Norther Empire to the east and it would freeze, I relaunched the game and loaded the save and moved to the same place again and it froze almost at the same spot. Then I decided to move west instead and it did not freeze for a while.