Similar to this:
MCPE-44486
Which was not reproducible.

It makes the game unplayable when the item in your hand randomly changes.
What I figured out is that it is the Oculus laser beam from right controller interacting with the HUD, when I think it should not.
Was able to alleviate this issue by a setting to put HUD in "off hand". This resolves the issue for me it seems, but I'm sure others have not found this solution.