[trinity-users] Problem with twin and recent Firefox repainting when switching desktops

When switching virtual desktops back to the one where Firefox is open, when certain pages are displaying on the active tab, the window contents do not repaint until moving the mouse over a mouseover effect (e.g. a hoverable link) changes the window status. The window then shows its contents. This started for me with Firefox 73, got somewhat better with Firefox 74 (could only reproduce it on one page, a specific Vbulletin forum listing) and got worse than ever with Firefox 75. Now it happens with most pages that have a list of hoverable links. For example Vbulletin forum listings, and even https://www.kernel.org This does not happen with Fluxbox, seems to be only with TDE/twin. I can reproduce it on both my Manjaro and Linux From Scratch systems. I thought maybe enabling the compositing ("composition manager") might help with this (I build support for it, but I don't enable it) but it neither helps nor harms. A previous cause of this in Firefox was "focusmanager.testmode" but that's set to false now and not applicable. Anybody else seeing this behaviour, or know of any settings or command line arguments for twin that might change this paint behaviour? Thanks,