"Unexpected path length 4 for exit circuit 4841, purpose 5"

Some bridge operators reported seeing these lines in their relays log running 0.4.7.7:

May 20 07:29:46.000 [notice] Unexpected path length 4 for exit circuit 4841, purpose 5
May 20 08:59:48.000 [notice] Unexpected path length 4 for exit circuit 4878, purpose 5
May 20 10:30:49.000 [notice] Unexpected path length 4 for exit circuit 4904, purpose 5
May 20 12:00:51.000 [notice] Unexpected path length 4 for exit circuit 4932, purpose 5

https://forum.torproject.net/t/unexpected-path-length-4-for-exit-circuit-x-purpose-5/3305