rncbc.org a.k.a. Rui Nuno Capela

As it seems you have jack1 built from source and installed in /usr/local. Is it possible you have a previous libjack installation under eg. /usr ?? That might be a concern, as it reads from the stack trace above, qjackctl is dying due on a segfault inside jack client thread, which may infer some linkage mismatch (jackd and qjackctl linked to different libjack instances).

Make sure you uninstall any pre-packaged jack, before you build and install jack from source again. BTW, which version of jack1 ?

HTH