Since the last Plex Media Server update (or maybe it was a chrome update?) if I pause and try to resume a minute or 3 later it will not unpause. I can simply shift-left and it will resume though. (I assume shift right works, too)
This also not seem to be an issue with the plex web (plex.tv/web/app) but I'm too lazy/disinterested to enable UAC to see if it's an issue in the 8.1 app. Since all the extra features don't work in there I'm even less inclined to find out.