I have the same network, and I ran into the exact same issue with my HB3, 6 S330’s, 1 E330. I have 4 APs around the house and 6 VLANs.
I tried just about everything and finally rebound my E330 and it worked!
Initially, I thought it wasn’t truly successful. The E330 was unresponsive after setup, and it fell off the network. After a few minutes, it “woke up” and hopped over to an AP that was further away (which was odd) but it has stayed locked on there for at least several minutes so far. I’m able to stream video and do other stuff just fine with it but haven’t tested everything yet. So far the E330 has transmitted 32MB, according to Unifi console.
Eufy app was just updated in the last 24 hours (not sure if it affects this) for iOS (unsure about Android).
E330: system 0.5.7.4, subsystem 18137
HB3: system 3.3.2.5, subsystem 1.4.0.8
Eufy app: 4.7.4_1323
