hi bluelupo,
i do not have any core dump, but in dmesg i find the following entry:
[ 5551.320574] kactivitymanage[16981]: segfault at 7fe66c036cd0 ip 00007fe660043471 sp 00007ffff8f989e8 error 4 in libQt5Sql.so.5.6.1[7fe66002d000+45000]
if you can let me know what other logfiles are interesting, will post these, too.
best
absolut