Description of problem:

The context menu is sometimes (+- 50%) invisible.  The menu does react to clicks and keyboard shortcuts, and often when dragging the mouse over the menu the menu suddenly appears.

This applies to the menu on the tabs (close tab, pin tab,...) and menus inside web pages (copy, paste, ...)

the menu is in the correct spot


Version-Release number of selected component (if applicable):

firefox-81.0.1-5.fc33.x86_64
wayland


How reproducible:

It happens more or less 50% of the menus attempted.  Cancelling the menu (escape, or left click elsewhere) and trying again often displays the menu.

It *seems* to happen more often if the machine is busier.  It *seems* difficult to replicate when the machine is completely idle.  It's > 90% when "busy".

"busy" means a lot of cpu, and load average between 1 and 2.


Steps to Reproduce:
1. start firefox
2. open any web page
3. right click


Actual results:

menu is invisible, but does react to shortcuts and clicks


Expected results:

menu is visible.


Additional info:

single monitor, lo-dpi (1080p), wayland

Since it could be driver related, lspci for video:
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 5500 (rev 09)
0a:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Topaz PRO [Radeon R5 M255]

No add-on closed-source drivers installed, just stock Fedora.