Every now and then face flexes break/all stack up on one flex and require a reload to fix things with the exception of the eye sliders.
The eye flexes have been broken since the introduction of Gmod 13 with no fix in sight, no pun intended.
On a semi-related note, you can dl an addon called "HWM Face Poser Fix" off the workshop
. It'll set flexes like "mouth sideways", "jaw sideways" and the like at 0.5 so you don't get an oddly shaped face when you select a model with the faceposer.