I've exactly the same issue !
Everytime i win a siege in a NPC town, the loading screen appear and the load never begin.
For exemple, after a battle of 3 hours in Welgeth, at the beginning all my units were lvl 5, after lvl 17, the game freeze at loading screen (only soud remain) and i was obligated to restart the game for discover my armie remaining lvl 5... Help, that's horrible :'(
My username is Kolldor
Here are my logs: