open the offending .qtr file and when it stops here eventually on segfault:
gdb> bt
an immediate stacktrace is dumped and check where and what's the offending crash point (should point to which plugin, library or code that is segfaulting.
once you find the culprit, try to edit the .qtr file and remove the suspect sections, assuming it's one or more plugins that is causing trouble.
most probably it's a rogue VST plugin...
you can run from the console under gdb:
gdb/path/to/qtractorgdb> runopen the offending .qtr file and when it stops here eventually on segfault:
gdb> btan immediate stacktrace is dumped and check where and what's the offending crash point (should point to which plugin, library or code that is segfaulting.
once you find the culprit, try to edit the .qtr file and remove the suspect sections, assuming it's one or more plugins that is causing trouble.
hth.
cheers