I also see a lot of these errors here on Wily at KDE Plasma:

Application: Plasma (plasmashell), signal: Segmentation fault
Using host libthread_db library "/lib/arm-linux-gnueabihf/libthread_db.so.1".
__libc_do_syscall () at ../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46
[Current thread is 1 (Thread 0xb2ad9000 (LWP 4363))]

Thread 14 (Thread 0xb076a3e0 (LWP 4365)):
#0  __libc_do_syscall () at ../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46
#1  0xb55706b0 in __pthread_cond_wait (cond=0xc0560, mutex=0xc0548) at pthread_cond_wait.c:186
#2  0xb2296592 in ?? () from /usr/lib/arm-linux-gnueabihf/dri/swrast_dri.so
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 13 (Thread 0xaff6a3e0 (LWP 4366)):
#0  __libc_do_syscall () at ../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46
#1  0xb55706b0 in __pthread_cond_wait (cond=0xc0668, mutex=0xc0650) at pthread_cond_wait.c:186
#2  0xb2296592 in ?? () from /usr/lib/arm-linux-gnueabihf/dri/swrast_dri.so
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 12 (Thread 0xaf76a3e0 (LWP 4367)):
#0  __libc_do_syscall () at ../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46
#1  0xb55706b0 in __pthread_cond_wait (cond=0xc0770, mutex=0xc0758) at pthread_cond_wait.c:186
#2  0xb2296592 in ?? () from /usr/lib/arm-linux-gnueabihf/dri/swrast_dri.so
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 11 (Thread 0xaef6a3e0 (LWP 4368)):
#0  __libc_do_syscall () at ../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46
#1  0xb55706b0 in __pthread_cond_wait (cond=0xc0878, mutex=0xc0860) at pthread_cond_wait.c:186
#2  0xb2296592 in ?? () from /usr/lib/arm-linux-gnueabihf/dri/swrast_dri.so
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 10 (Thread 0xae7143e0 (LWP 4369)):
#0  0xb56904e0 in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0xb6bb4168 in ?? () from /usr/lib/arm-linux-gnueabihf/libxcb.so.1
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 9 (Thread 0xad1c43e0 (LWP 4377)):
#0  0xb5a03d80 in QTimerInfoList::timerWait(timespec&) () from /usr/lib/arm-linux-gnueabihf/libQt5Core.so.5
#1  0xb5a04c52 in ?? () from /usr/lib/arm-linux-gnueabihf/libQt5Core.so.5
#2  0xb4fb0c54 in g_main_context_prepare () from /lib/arm-linux-gnueabihf/libglib-2.0.so.0
#3  0xb4fb12ee in ?? () from /lib/arm-linux-gnueabihf/libglib-2.0.so.0
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 8 (Thread 0xaad3d3e0 (LWP 4378)):
#0  __libc_do_syscall () at ../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:47
#1  0xb56a011a in __GI___clock_gettime (clock_id=0, tp=0xaad3cbec) at ../sysdeps/unix/clock_gettime.c:99
#2  0xb59095b2 in ?? () from /usr/lib/arm-linux-gnueabihf/libQt5Core.so.5
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 7 (Thread 0xa8fe23e0 (LWP 4386)):
#0  0xb4fb13c2 in ?? () from /lib/arm-linux-gnueabihf/libglib-2.0.so.0
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 6 (Thread 0xa7dff3e0 (LWP 4387)):
#0  0xb56904e2 in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0xb4fb137a in ?? () from /lib/arm-linux-gnueabihf/libglib-2.0.so.0
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 5 (Thread 0xa6a3e3e0 (LWP 4388)):
#0  __libc_do_syscall () at ../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46
#1  0xb55706b0 in __pthread_cond_wait (cond=0xb6f23dd0, mutex=0xb6f23db8) at pthread_cond_wait.c:186
#2  0xb6ebfe76 in ?? () from /usr/lib/arm-linux-gnueabihf/libQt5Script.so.5
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 4 (Thread 0xa4eff3e0 (LWP 4389)):
#0  __libc_do_syscall () at ../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:47
#1  0xb56a011a in __GI___clock_gettime (clock_id=0, tp=0xa4efebb4) at ../sysdeps/unix/clock_gettime.c:99
#2  0xb59095b2 in ?? () from /usr/lib/arm-linux-gnueabihf/libQt5Core.so.5
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 3 (Thread 0xa40633e0 (LWP 4391)):
#0  __libc_do_syscall () at ../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46
#1  0xb55706b0 in __pthread_cond_wait (cond=0x32e118, mutex=0x32e100) at pthread_cond_wait.c:186
#2  0xb58a52f8 in QWaitCondition::wait(QMutex*, unsigned long) () from /usr/lib/arm-linux-gnueabihf/libQt5Core.so.5
#3  0xb69b710a in ?? () from /usr/lib/arm-linux-gnueabihf/libQt5Quick.so.5
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 2 (Thread 0x9c9723e0 (LWP 4393)):
#0  0xb56744e0 in nanosleep () at ../sysdeps/unix/syscall-template.S:81
#1  0xb56742bc in __sleep (seconds=0) at ../sysdeps/unix/sysv/linux/sleep.c:138
#2  0xb6f77864 in ?? () from /usr/lib/arm-linux-gnueabihf/libKF5Crash.so.5
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Thread 1 (Thread 0xb2ad9000 (LWP 4363)):
#0  __libc_do_syscall () at ../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:46
#1  0xb55706b0 in __pthread_cond_wait (cond=0x135a428, mutex=0x135a410) at pthread_cond_wait.c:186
#2  0xb58a52f8 in QWaitCondition::wait(QMutex*, unsigned long) () from /usr/lib/arm-linux-gnueabihf/libQt5Core.so.5
#3  0xb69b4e4e in ?? () from /usr/lib/arm-linux-gnueabihf/libQt5Quick.so.5
Backtrace stopped: previous frame identical to this frame (corrupt stack?)