Problem with BE11000/BE65 router, satellite keeps disconnecting
I recently got my BE11000/BE65 3-pack system from Costco. The system has been super unstable after installation. I have them all hardwired to a switch, and all 3 units are set in access point mode. However, two satellites keep dropping connection. They show red in status light so I assume even the WIFI is not working on them. Connection count from the main unit (which is working) is suspiciously low and I'm missing about 10-20 clients from the diagram, but the whole-house WIFI and IoT devices seems to be functioning normally.
I'm using ethernet backhaul and my unit setup is in the first diagram. I'm using a TP-Link 2.5G unmanaged switch (TP-Link TL-SG108S-M2), and my main router is TP-Link ER707-M2. I'm pretty confident my connection is correct. The firmware on my units is "1.0.5 Build 20240521 Rel. 64384".
Scratched my head off and couldn't figure out why. Any help or suggestion would be greatly appreciated!