That depends, it could be the unraid API docker crashing, it could be the mqtt broker crashing. Or if the HA restarts while the API is still running it will take up to an hour by default to refresh all the states.
There could also be a few other reasons, if you could give me some more information that would be helpful. Like does it happen at a certain time or when you do a certain thing, does it come back after a certain amount of time etc.
Cheers