Intermittent test failures in relay/close_circ_rephist

I observed this failure once out of about 10 tests when testing legacy/trac#29541 (moved) on commit:

commit 5614960e94 (HEAD, tor-github/pr/723/merge)
Merge: 69238ca2da 065e7da8e6

Here is the test error:

relay/close_circ_rephist: [forking] 
  FAIL ../src/test/test_relay.c:127: assert(find_largest_max(write_array) OP_EQ 2*(get_cell_network_size(nchan->wide_circ_ids) +TLS_PER_CELL_OVERHEAD)): 0 vs 1082
  [close_circ_rephist FAILED]

It looks like this test was introduced in legacy/trac#23512 (moved) for Sponsor Q. Is Sponsor Q still open?

Is it an obvious fix? If not, let's see if it happens again.