This seems to be a regression of [Link Removed]? Difficult to say.
Originally reported here: https://udn.unrealengine.com/questions/391665/animcurve-parameter.html
Open included project.
Open TestEyeAnim map.
The skeletal mesh has 2 animations, one that updates animation curves, another that has no curves. You can play and and use Y and T to switch between the animations - logic for this lives in the Level Blueprint.
Oddly enough, if you use SetAnimation nodes, the material values fall back on 0.f and DO NOT ANIMATE. Is this a separate bug?
If you use PlayAnimation instead, the materials use the last value found on the curve, which causes the animation to appear as if paused.
You can swap between Set and Play Animation by plugging in the alternate nodes in the Level Blueprint
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-49724 in the post.