Same over here. This bug has been in there since day one. I have already mentioned it on the Plex HTPC feedback thread about a year ago. (multiple times even) Plex HTPC feedback - #472 by Mitzsch
Well and its also present in the LG Smart TV app. I opened a thread in the TvAPP part and a Plex employee already noticed. Maybe there is hope that it will be also fixed in Plex HTPC.
