[tor-relays] scale_active_circuits assertion fail

[Logforme]

My relay (855BC2DABE24C861CD887DB9B2E950424B49FC34) just crashed with 
the following error:
Feb 20 14:33:40.000 [err] tor_assertion_failed_(): Bug: 
../src/or/circuitmux_ewma.c:711: scale_active_circuits: Assertion 
e->last_adjusted_tick == pol->active_circuit_pqueue_last_recalibrated 
failed; aborting. (on Tor 0.3.2.9 )
Feb 20 14:33:40.000 [err] Bug: Assertion e->last_adjusted_tick == 
pol->active_circuit_pqueue_last_recalibrated failed in 
scale_active_circuits at ../src/or/circuitmux_ewma.c:711. Stack trace: 
(on Tor 0.3.2.9 )
<snip stack trace>

The relay had been up for 23 days:
Feb 20 12:55:12.000 [notice] Heartbeat: Tor's uptime is 23 days 17:59 
hours, with 30352 circuits open. I've sent 20574.36 GB and received 
20125.28 GB.

When I checked htop earlier everything looked fine. Modest CPU and MEM 
usage.

What went wrong and what can I do to prevent this from happening again?