What gameplay feature is this bug affecting?
Userlog

What's the issue? Please include any error messages you receive and as much detail as possible.
Quest is marked as completed twice in the userlog.

Any links relating to this bug? For example, if a particular lion is bugging, what is the link to that lion?
https://www.lioden.com/userlog.php?id=121082

Any screenshots you can provide us with?
https://i.imgur.com/W4sGxcR.png

Please provide us with step by step explanation how this bug happened so we can attempt to replicate it. If it's complex, please include screenshots where possible:
Completed the quest for Bast and went to check on something in userlog and noticed it appeared twice.

It did not give double the KB (+20, rather than +10) modbox implied, merely seems to be a userlog issue.