I've already reported about this before, don't know if they registered as a bug, so I made a video demonstrating.

The problem happens on mobile when there is a lot "sub-menu".

 

 

Thank you for reporting this. I can confirm that we have an active internal bug report for this issue and our developers will review it. A fix should be available in a future maintenance release. Thanks again!

This issue has been resolved in 4.6.12, which has just been release. Please let us know if you still have any issues once you have upgraded to that release.