I've used the USSEP throughout several gameplays already but this is the first time I encountered this bug, so there's probably an underlying trigger which I haven't been able to pinpoint (yet).
When on the quest Blood on the Ice (quest ID MS11), stage 60, the objective is to look for clues in Hjerim (Windhelm). Normally, the player needs to "inspect" several items (item IDs below) in the house to advance this objective, but in this case there was no inspect trigger displayed so no interaction was possible.
I've narrowed the issue down to the USSEP mod as it still persists with no other mods active (both with and without SKSE). Tried leaving Hjerim, completing a few quests in Windhelm and all over Skyrim and coming back, with no result. Only disabling USSEP fixes the issue.
The game doesn't crash, but the quest can't be progressed without disabling USSEP to inspect the items before turning it back on.
I've attached my save inside Hjerim with no mods enabled except USSEP, at quest stage 60. If you need more details or anything, feel free to contact me.
Great job folks, keep up the good work
IDs of to be inspected items:
Ground floor:
- Small cabinet with "Beware the Butcher" pamphlets: 000df5a8
- Strange amulet: 000814b3
- Closet: 000df5a9
- Wardrobe: 000df5a4
- Altar: 000d55f8
- Chest: 000eoe51
- Pots & Pans: 000df543 / 000d55f8
First floor:
- Beds & chairs: 000df556 / 000df557 / 000df558