The quest chain for "Plaque of Sotek" stops after completing the amass 5000 treasury step when not playing as cult of sotek.
I think this is because the next step would require the sacrifice mechanic witch is exclusive to cult of sotek.
Maybe it is possible to make the quest chain skip that step instead of just not progressing when the faction is not cult of sotek.
In this screenshot you can see the quest step complete but not trigger the next step.
(I completed the previous step the same turn so that is the top set of completed/issued.)
Build nr: 11694.1746401
The save file is one turn after because i wanted to see if it would still trigger the next turn.
I hope this information helps and this can be fixed soon as it made me kind of sad to lose such a powerful item to this bug.
Edit: added my empty modified.log