Coukd be relays, could be a bug (occasionally Coracle will get stuck and drop a note, on my list). It could be a flaky query, so try looking for it on multiple clients
Coracle is developed by nostr:npub1jlrs53pkdfjnts29kveljul2sm0actt6n8dxrrzqcersttvcuv3qdjynqn and snort by nostr:npub1v0lxxxxutpvrelsksy8cdhgfux9l6a42hsj2qzquu2zk7vc9qnkszrqj49 . Perhaps they might be able to help you better with it.
One thing to check is the relays that you read and write too - but the devs would know best
Discussion
Had similar kinda issue on Primal yesterday, where refreshing helped.
Similar to a timeout or smth, weird