Server sometimes doesn't send flea sell callback

[DrakiaXYZ]

Reported via Lacy, sometimes the server isn't sending back the necessary trigger for a flea sell to make the client call the callback. Very rare, but want to log it incase we can track it down

[Lacyway]

Hard to reproduce. Easiest way is to use a mod to post several items at once.

[ArchangelWTF]

I shat out some tests with ChatGPT and found some issues with locking in RagfairOfferHolder, I fixed those in 8d9f4d4