Cancels/trades missed by the contract observer result in outdated orders in the book.

[mmhh1910]

Currently freeatnet sorts this out manually (after a downtime) by running the script: https://github.com/forkdelta/backend-replacement/blob/master/app/src/contract_events_backfill.py

This should either be done automatically or freeatnet suggested:

"I would implement periodic orderbook refreshes, on per token basis or just queueing older orders to be refreshed automatically whenever they're returned to people."