I have the same problem with a roborock s7 and unifi u6-lite access point. Tried various different settings in unify but it doest actually seem to be a connection issue from the ap, maybe a powersaving thing on the roborock?
At the same time a roborock s5 does not suffer this problem and seems to be stable.
I “fixed it” by restarting all the network, so my UDM Pro, Unifi Switch and Unifi AP (hd-Nano). Give it a try, if it doesn’t work I can add screenshots of my config, which is nothing fancy tbh