I forgot to mention that I tested this with yEd 3.6 and 3.8 and both freeze.
an strace halts at
rt_sigaction(SIGINT, {0x43e700, [], SA_RESTORER, 0x7f7bffff2b80}, {SIG_DFL, [], SA_RESTORER, 0x7f7bffff2b80}, 8) = 0
wait4(-1,
So, it waits for something. I guess it's some concurrency bug.