Tried to establish rendezvous on non-OR circuit with purpose Acting as rendevous (pending)

Some relays have been getting this warning for the past few days. It's unclear what's causing it.

From briefly reading the code, it seems like someone is trying to establish an RP on the relay, while he has already asked the relay to be an RP in the same circuit. I'm not exactly sure if that user can succeed in establishing multiple RPs in one circuit. That is, it's still unclear whether this is a Tor client bug, or maybe a DoS attacker.

We should probably look into this message a bit more.