MotionManager won't appear

Hi,

I made an assembly and then started doing a motion study. Normally whenever I click the "Motion Study 1" tab (or whatever the tab is named), the motionmanager appears. However, after using the file for a while (range is unpredictable, maybe 30 mins later, day, week) if I leave the motionmanager and try to click the tab again, the motionmanager doesn't appear. If it helps at all, sometimes when I click the tab a scroll bar <where the feature tree in the motionmaanger would be> appears for a few seconds before disappearing.

I tried googling but couldn't find any help. I attached a couple images showing what what happens. This problem has happened 5 times before for me.

Any help would be appreciated.