For some reason, stealth seems to bug pretty often. After a while (but not always) and especially after transitioning from one area to the other, stealth skills drop about 4 points lower.
This is fixed by re-equipping armor. It doesn't work by simply re-equipping trinkets.
Do you have ranger levels? If so you are only supposed to get the bonus in "wild" areas, so it is likely just correcting itself.
Remember to post character name / details when tossing out bug reports.