Well.. It happened again a few times.
The most recent one happens when I was doing a meph run. The run usually takes 2 minutes max all-included, and the shield was gone in the midst of the fight. I did get hit at the time.
FYI, the shield was supposed to last 924 seconds...
There is one more explanation left - I might have forgotten to turn it on :lol:
I'm just wondering if this happens to anyone else or not, if not, it might be just me being careless.