I use vanilla v1.6 game, no mods, PC/Win 10.
Tonight I was talking to Theresa (in the courtship quest chain). When you have the option to give her an item as a gift, it had boar tusks or dagger available.
I chose boar tusks, but hit esc to try and select a jewelry item from my inventory as this seemed a much more sensible option having talked to girls in real life ;). I think that may have broken things a little.
After selecting a ring from inventory and clicking X to confirm delivery, the menu disappeared and I was unable to progress or quit the conversation. I used ‘quit’ in the console to exit, losing 1.5-2 hours worth of gameplay.
It is a bug. Happens too often on PC and console. After my 3rd gift the game locked. I had to shut down wait 2 min before restarting.