I've noticed something occur three times yesterday, and that finally led me to (yes, I'm admitting it) log out during a combat. Yesterday was the first time I've ever noticed this, so I'm not sure if it is new or what.
In wandering the wilds, my character was nailed by a web shot by a spider/ettercap group (not sure whose it was that hit me). After combat was over, I noticed my AC had dropped by half (yikes), even after several minutes of just sitting. I experimented with checking for unusual after effects (none), unequipping and re-equipping, and so forth - no change. Logging out and back in changed it back to normal. Continuing on, I was nailed again by a spider and the same thing happened. Again, the only fix was logging out and back in.
Continuing on, I was in-game for some time and had gone through several more combats (including spiders again) until I got into it with some kobolds and an umber hulk in the mines, who proceeded to rock me abnormally hard and fast until I clicked on my INV for a potion and saw my AC was back down to 10 (having neglected to look after my last spider encounter). At this point, near death, I logged, knowing that the next volley with that AC (over 10 points down from its norm) was going to fry me. I did not immediately log back in as I knew that although my AC would be fixed, they would get at least one "free swing" and likely kill me.
So within the bug report (I am willing to test this again, and will probably do so tonight), I need to ask the question: What's the DM opinion of my bug-out due to an artificially gimped AC? If it's a no-no, I'll bend over and take it next time (even from a bunch of #$%#$ kobolds who shouldn't be able to hit the broad side of a barn).
Thanks!