I've been seeing this for years and have been unable to fix it, although the great news is that I haven't seen it since about the May or June updates. So fingers crossed, maybe it's gone. It was never a permanent problem - if you save the project and re-open it the UAD meters start working again.
There still seem to be oddities with SPLAT and some plugin UIs, for example VacuumSound do a free ADT plugin that simply won't display a proper UI although it all works fine with Reaper.