https://github.com/Baron-von-Riedesel/JWasm
might it be possible for you to upload the latest source code (2.12 pre)? Yes. See...
I have no free time for jwasm issues for the next months.
Intel docs marks JMP r/m32 as N.S. in 64-bit code ( which I guess means "not supported"...
In 64-bit, you must be careful with push/pop if you used OPTION WIN64:2 in your source....