Hi, I have a similar issue. On my current buster installation (everything is up-to-date) Insync wont start. The output of the given command reports this:
Warning: Ignoring XDG_SESSION_TYPE=wayland on Gnome. Use QT_QPA_PLATFORM=wayland to run on Wayland anyway.
INFO 2018-12-07 10:26:27,808 [main__insync:main:105] insync version: 1.5.5.37368
INFO 2018-12-07 10:26:27,810 [main__insync:main:106] client created <ideskmain.client.Client object at 0x7fcb40102bd0>
INFO 2018-12-07 10:26:27,811 [unix_socket_server_portable:start:49] unix socket server thread start
INFO 2018-12-07 10:26:27,811 [main__insync:main:114] starting client
INFO 2018-12-07 10:26:27,816 [fswatch:_start:532] LinuxFSWatcher._start
INFO 2018-12-07 10:26:27,817 [fswatch:_pull_loop:267] Inotify loop enter
Received signal 11 SEGV_MAPERR 000000000108
#0 0x7fcb46da3c1f
#1 0x7fcb457cca9d
#2 0x7fcb46da412e
#3 0x7fcb6ce978e0
#4 0x7fcb60268b24
#5 0x7fcb60269da8
#6 0x7fcb6aef5dd4 glXCreatePbuffer
#7 0x7fcb4582fc89
#8 0x7fcb4581aa08
#9 0x7fcb478e945d
#10 0x7fcb45b24f11
#11 0x7fcb45b26705
#12 0x7fcb47d9f857
#13 0x7fcb495b9795
#14 0x7fcb46e0c5d5
#15 0x7fcb46e07970
#16 0x7fcb6ce8cf2a start_thread
#17 0x7fcb6ca03edf clone
r8: 0000000000000000 r9: 0000000000000001 r10: 00007fcb6ca42770 r11: 0000000000000206
r12: 00005610a8e73440 r13: 00005610a9007c10 r14: 0000000000000005 r15: 00005610a8eaa450
di: 00005610a8e73440 si: 0000000000000000 bp: 00005610a8e73440 bx: 0000000000000000
dx: 0000000000008041 ax: ffffffffffffff50 cx: 0000000000000000 sp: 00007fcaddffa480
ip: 00007fcb60268b24 efl: 0000000000010202 cgf: 002b000000000033 erf: 0000000000000004
trp: 000000000000000e msk: 0000000000000000 cr2: 0000000000000108
[end of stack trace]
Calling _exit(1). Core file will not be generated.