Low Item buff doesn't expire w/GM buffs

Description of the bug: (optional screenshot/video):

The green gem item buff (forget what it's called) was blinking from the time it was supposed to expire until the GM buffs expired (instead of expiring on time). This only happened when I had GM buffs on afaik.
What is supposed to happen?:
The item is supposed to expire on its own time (20mins) instead of waiting for GM buffs to end.

In the screenshots: over the course of 3 mins the item was blinking but did not expire. (this continued for longer but I don't have another ss) The item is definitely in effect as it is the only thing giving me an attack buff, which is why the attack stat is red.

 

afaik GM buffs don't give w. att?
This is a pretty weird item, given that it gives a few different stats a buff. I kind of expected to be getting just the w. att from it while everything else is overwritten by GM buffs, which is what seems to be the case.
Anyway, I personally don't mind the extra time with it, but I thought maybe this could happen with other items which might not be what you want.