For the next beta, we've made a change to increase the default timeout on directory reads, and also tie it to the long_operation_notify_time setting in Preferences in case you need to increase it further.
Ah-ha! You're already on it; excellent
I came here to say exactly the same as the OP.
I've installed 13.2 and the behaviour is better. I get the 'An operation is taking longer...' message or whatever it says, but DO doesn't just give up like it did. My NAS comes online just a moment after the message and DO shows the folder; no change to the timeout needed. That's fine.
Thanks for the quick fix
Glad it's working now! Thanks for taking the time to let us know.