There's definitely a bug, whether or not it's just a display bug remains to be seen, but I notice, when running BAM with my enchantment focused sorcerer, that the duergar were saving a bit more often than I remember they should.
Typically this means I've forgotten to re-equip my +CHR helmet and still have my +CHR/Haggle helmet equipped.
Simple enough, I switched to my +CHR helmet.
Then I checked, on a hunch, my spell DCs.
Suggestion: DC 13 instead of 27
Charm Monster: DC 14 intead of 28
It appears, at the very least, there's a display bug when swapping +caster stat items, but it does jibe with my anecdotal experience that sometimes it's nearly impossible to land a spell that typically lands 80%+ of the time, and swapping items back and forth sometimes "fixes" that.
So it's nice to see that maybe it's not just my imagination.
BTW this is easily tested by checking your spell DCs, swapping a +caster stat item in or out and rechecking your save DCs.
Hopefully it's just a display bug, but if it isn't...
****.