5.6.0.15 Filter box intermittently disappears

After I close RDM to tray for a while and try to restore, occasionally the filter sessions box doesn't appear. I still see the icon and the Clear button, but the textbox itself doesn't reappear. This happened once yesterday and twice today, but I never noticed it in any of the other betas. When it happened yesterday I had to restart RDM to get it back. Today one time I had to restart, the other time it took about 2 minutes before it came back. I'm not sure what could be causing this, but I'm pretty sure I had the box clear when I was closing to tray.