Not sure yet if this is caused by "xpra info" or the new jpeg codec (#1423).
This a server crash, I cannot reproduce it with the python client with "--encodings=jpeg" which is strange. To trigger it with the html5 client, run "glxspheres" and from any other terminal:
while true; do xpra info |>& grep fps=; done
Problem identified, this is a dupe of #1430
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1452