Tested with qutebrowser 1.6.2 and falkon 3.0.1.
I upgraded from Qt 5.9.7 to 5.9.8 last weekend and found that when ebay.com or ebay.co.uk load I get a message that the renderer crashed in qutebrowser and that the page couldn't be displayed (or similar) in falkon. The crash isn't instantaneous - I see the page loading all the content and then it crashes right at the end.
Testing with --qt-flag single-process seems to be a workaround in qutebrowser, but it doesn't look like falkon supports passing flags to Qt.
Unfortunately I don't have enough resources to build Qt with -debug, and ld gets OOM killed after eating all my RAM. This is the only output, if it's any help:
Received signal 11 SEGV_MAPERR 000000000000
#0 0x7f587804c29e <unknown>
#1 0x7f587804c659 <unknown>
#2 0x7f587489d3b0 <unknown>
r8: 00000b72d9404000 r9: 000010ad5f402538 r10: 0000000000000007 r11: 00000000000000ff
r12: 00007f587d974808 r13: 0000000000100000 r14: 0000295c5fe42628 r15: 00007ffc752d2938
di: 0000000000000002 si: 00007ffc752d2524 bp: 00007f587c0a04bc bx: 00007f587d973040
dx: 0000000000000000 ax: 0000000000000001 cx: 0000000000000000 sp: 00007ffc752d2518
ip: 0000000000000000 efl: 0000000000010202 cgf: 002b000000000033 erf: 0000000000000014
trp: 000000000000000e msk: 0000000000000000 cr2: 0000000000000000
[end of stack trace]
Let me know if there's anything else I can add.