The "starter" Spiked Turban granted by using Stone of Experience incorrectly stacks with Greater Stability. This behavior was observed on live servers just before U15.
(This might apply to non-starter version and also possibly other resistance items, but I have not tested)
Bug as seen in the in-game log:
spiked turban provides the following bonuses:
+3 enhancement bonus to fortitude saves
+3 enhancement bonus to will saves
+3 resistance bonus to reflex saves
As once leaked by a dev, most items that claim to provide a "resistance" bonus to saves in their description are internally coded to grant "enhancement" bonus. This is not the case for Spiked Turban's reflex save bonus. As a result, you can get a +3 stacking bonus to reflex saves from spiked turban.
1. Undress your character.
2. Wear a Greater Stability armor. Note the reflex save.
3. Wear Spiked Turban. Note that reflex save is increased by 3.
4. Optionally, look at the in-game log for information about stacking.
As I haven't tested other Resistance items, I am not filling a bug report, because I am not sure if it's a bug of Spiked Turban or Resistance items in general.