Ok I tried again with Qt 5.9.5. Unfortunately i get another segfault:
[ 176.513125] SVPManager[3695]: segfault at 8 ip 00007f1d16d64db9 sp 00007ffefdd94350 error 4 in libQt5Widgets.so.5.9.5[7f1d16bc9000+62d000]
It's also really irritating to me that only the SVPcode extension is affected.