Please fix that ticket:2301#comment:24
It's been happening for ever, and in Xpra-Python3-x86_64_4.0-r25568 too.
Using the "stable" 3.0 xpra (r24xxx) is the only workaround
Fixed in r25601.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2631