Assertion `ticks_now == trace_ticks' failed to hold. ticks mismatch for 'SYSCALL: munmap'; expected 106734163, got 106734145

I get the following when trying to replay a recording of Firefox on Ubuntu 19.10

FATAL /build/rr-Stwazj/rr-5.2.0/src/ReplaySession.cc:1023:check_ticks_consistency()] 
 (task 20251 (rec:18138) at time 5571)
 -> Assertion `ticks_now == trace_ticks' failed to hold. ticks mismatch for 'SYSCALL: munmap'; expected 106734163, got 106734145
=== Start rr backtrace:
rr(_ZN2rr13dump_rr_stackEv+0x41)[0x55cc30ebb581]
rr(_ZN2rr9GdbServer15emergency_debugEPNS_4TaskE+0x605)[0x55cc30debdd5]
rr(_ZN2rr21EmergencyDebugOstreamD2Ev+0x122)[0x55cc30dfbe82]
rr(_ZN2rr13ReplaySession23check_ticks_consistencyEPNS_10ReplayTaskERKNS_5EventE+0xaa)[0x55cc30e65f2a]
rr(_ZN2rr13ReplaySession11replay_stepERKNS0_15StepConstraintsE+0x84e)[0x55cc30e6bf1e]
rr(_ZN2rr14ReplayTimeline19replay_step_forwardENS_10RunCommandEl+0xce)[0x55cc30e828de]
rr(_ZN2rr9GdbServer12serve_replayERKNS0_15ConnectionFlagsE+0x85)[0x55cc30deec25]
rr(+0x10c7a7)[0x55cc30e627a7]
rr(_ZN2rr13ReplayCommand3runERSt6vectorINSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEESaIS7_EE+0x750)[0x55cc30e63310]
rr(main+0x282)[0x55cc30da6992]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xeb)[0x7f205f1bfb6b]
rr(_start+0x2a)[0x55cc30da6aaa]
=== End rr backtrace
Launch gdb with
  gdb '-l' '10000' '-ex' 'set sysroot /' '-ex' 'target extended-remote 127.0.0.1:20251' /home/jrmuizel/.rr/firefox-0/mmap_hardlink_3_firefox

Start with src/ReplaySession.cc:1023 and the check_ticks_consistency() call in replay_step(). Reproduce the Firefox recording on Ubuntu 19.10 using the provided gdb launch command, then inspect the SYSCALL: munmap event and the reported tick values. Done means identifying and correcting the cause of the replay tick mismatch, with a regression test if the repository provides a suitable test location.