This is with 188.8.131.523, downloaded from plex.tv
I've got the app running on my second monitor. I usually maximise it (that's the Windows maximise, so the title bar is still visible) but something's broken and now I can't minimise or restore the window, the title bar is missing and cycling from normal mode to TV Full Screen mode to Full Screen Mode makes no difference. When I use the double-arrow icon in TV mode to return to desktop mode, the player is still in full screen mode with the double-arrow icon offering to allow me to exit full screen mode, but all it does is change the icon to the screen icon offering to let me enter TV full screen mode. Double-clicking in the vicinity of where the title bar should be does nothing (i.e. it doesn't restore the app to normal windowed mode)
The only way I can move the window is by hovering over the icon in the Windows task bar until the preview appears, then selecting the Move option from the context menu, and even then I have to use the cursor keys to attach the window to the mouse pointer as the window won't let me drag it anywhere. Note that the Restore, Minimise and Maximise options are all greyed out.
Once I've got the window on my primary monitor, nothing really changes. The title bar and min/restore/exit buttons are missing, I can't resize the window by dragging the borders because they don't respond. Entering TV Full screen mode does not resize the window to fill the screen. Exiting that mode moves the window back to the secondary monitor, and it's stuck in exactly the same way as before.
I've tried repairing the installation, uninstall/reinstalling and uninstalling, then deleting HKEY_CURRENT_USER\Software\plex.tv and reinstalling but it makes no difference.