Saw some discussions in PC EU Murkmire zone chat and was able to reproduce an issue where the stamina bar is not correctly updating on regen. So if you're sprinting then stop, it doesn't go up until you sprint again or crouch. Also able to get it to update on blocking.
Curious, are other people getting this issue? Are you using an UI addons like LUI Extended?
https://www.youtube.com/watch?v=Ndte22XPniA