[Evolution] Weird delay in preview..

[Anonymous Japhering <japhering gmail com>]

Evolution 3.40.1 (flatpak git668023c) 
System: 
   Kernel: 5.4.0-70-generic x86_64 bits: 64
   Desktop: MATE 1.22.2
   Distro: Linux Mint 19.3 Tricia
   
recently did the update and started seeing that frequently the preview pane does
not render until mouse is in the preview pane. 

So if I'm click on specific messages in the message list, the preview pain stays
blank until I move the mouse over it.

Conversely, if I select a message in the list pane, move mouse to the preview
pane and then arrow key for the next message, it renders immediately.  So it is
definitely something with the position of the mouse relative to the preview
pane.

System is basically idle,  plenty of memory available (not stepping off memory
to swap space), plenty of available bandwidth ( as of the beginning of this
message is was getting 870Mbps from the Google servers, 750Mbps from Office365).

In Evolution, I'm currently running 2 - Gmail,  3 - G-Suite, and 1 - Office 365
accounts.  

Any thoughts on how best to isolate?

Thanks