I am a new customer. I was running build 2848 as a trial before purchasing. When I purchased, I upgraded to build 2864 and started having a javascript error that I didn't before. After the initial event load, if I right-click on an event to get the context menu, I receive an error from the _onMainRightClick function because the calendar.getSelection() returns null. Ignoring the error and continuing to run still pulls up the context menu that functionally works.
I find that after the initial load, if I go left-click or right-click an empty cell, I have no issues. I can then right-click on an event without error. At this point I downgraded back to 2848 to resolve my issue.