I checked the source and it is base 64 encoded. https://www.base64encode.org/ You just need to insert \ ahead of the =.
Funny but Mike and I have worked on the same team. I just upgraded to Red Hat 8.4 and I see the same thing with the GUI. But sync does occur.
Looks like this is fixed in the 2.19.0.57 build. Thanks.
Delete after encoding does not work. Files remain.
I am seeing exactly the same behavior when I updated to SeaMonkey 2.49.1