Quest Issue: Ivan's Remains: box doesn't combine

[Corvida]

I have resolved the issue; it turns out that I somehow ended up with a "dusty old jawbone" which is a no-drop for a completely different quest... but has the exact same image. Once I figured that out, I went back to the river & got ahold of an actual "barbarian jawbone", and the box combined with no issue.

Since the other jawbone is no-drop, from a different quest, and I'm pretty sure I got it when I accidentally wandered into the bear cave, I opted to squirrel it away in the bank for now. :$