I think this bug was found and fixed in 6.4 development phase. But I'm not sure so:
Using lz compression on server self-made images (*), resulted with bad stride values (**). This caused spice-server to abort.
Fixed by not using lz compression for such images.
(*) if example for such images is wanted see comment #11
(**) if more information is wanted: stride > bpp*width, which spice treats as bad values for images that go through lz compression.