I had the same problem:
insync start --no-daemon
Warning: Ignoring XDG_SESSION_TYPE=wayland on Gnome. Use QT_QPA_PLATFORM=wayland to run on Wayland anyway.
INFO 2018-12-17 20:57:04,386 [main__insync:main:105] insync version: 1.5.5.37368
INFO 2018-12-17 20:57:04,389 [main__insync:main:106] client created <ideskmain.client.Client object at 0x7fbc806b68d0>
INFO 2018-12-17 20:57:04,390 [unix_socket_server_portable:start:49] unix socket server thread start
INFO 2018-12-17 20:57:04,391 [main__insync:main:114] starting client
INFO 2018-12-17 20:57:04,405 [fswatch:_start:532] LinuxFSWatcher._start
INFO 2018-12-17 20:57:04,408 [fswatch:_pull_loop:267] Inotify loop enter
Received signal 11 SEGV_MAPERR 000000000108
#0 0x7fbc863f4c1f
#1 0x7fbc84e1da9d
#2 0x7fbc863f512e
#3 0x7fbcac5c16b0
#4 0x7fbc9f859b24
#5 0x7fbc9f85ada8
#6 0x7fbcaa503dd4 glXCreatePbuffer
#7 0x7fbc84e80c89
#8 0x7fbc84e6ba08
#9 0x7fbc86f3a45d
#10 0x7fbc85175f11
#11 0x7fbc85177705
#12 0x7fbc873f0857
#13 0x7fbc88c0a795
#14 0x7fbc8645d5d5
#15 0x7fbc86458970
#16 0x7fbcac5b6fa3 start_thread
#17 0x7fbcac13c88f clone
r8: 0000000000000000 r9: 0000000000000001 r10: 0000000000000006 r11: 0000000000000206
r12: 000055afca8c0da0 r13: 000055afcaa58eb0 r14: 000000000000000b r15: 000055afca8f6bd0
di: 000055afca8c0da0 si: 0000000000000000 bp: 000055afca8c0da0 bx: 0000000000000000
dx: 0000000000008041 ax: ffffffffffffff50 cx: 0000000000000000 sp: 00007fbc297f9480
ip: 00007fbc9f859b24 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.