Qtractor segfaults when loading linuxsampler plugin [SOLVED]

I've been getting segfaults with Qtractor when trying to load the linuxsampler plugin ever since Qtractor 5.3. I rebuilt Qtractor today
with SVN 2742 and still get the problem. The scenario is:
o start qtractor, create midi track.
o attempt to select linuxsampler plugin for track, get segfault when hit OK

Here is a strace of the crash in case that is useful:

mmap2(NULL, 528384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0xab7be000
mprotect(0xab7be000, 4096, PROT_NONE) = 0
clone(child_stack=0xab83e2b4, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0xab83ebd8, {entry_number:6, base_addr:0xab83eb70, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}, child_tidptr=0xab83ebd8) = 21794
sched_setscheduler(21794, SCHED_OTHER, { 0 }) = 0
futex(0xa06944c, FUTEX_WAIT_PRIVATE, 3, NULL) = 0
futex(0xa06942c, FUTEX_WAIT_PRIVATE, 2, NULL) = 0
futex(0xa06942c, FUTEX_WAKE_PRIVATE, 1) = 0
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
+++ killed by SIGSEGV +++
Segmentation fault

I was intending to test the "state" restoration of linuxsampler which has not been working for me, so I had:

o built the entire drobilla-lad SVN 3982 (this includes lilv)
o built libgig, linuxsampler, qsampler, lscp SVN 2322

which is supposed to get the state restoration (i.e. get linuxsampler to reload the sample file you had loaded in a previous session). Obviously, cannot test this in qtractor right now. I'm running AVlinux 5.0.2.