I’ve got a job right now is experiencing issues as well. I’ve swapped out the gen 2 DoorBird 3 times now with a fourth coming Monday.
Several issues are the amount of time required between button push’s. Another is what revision of the product are on. The latest version they fixed the button contact, so now you can press anywhere and it works.
This unit is hardwired with a Poe injector and has issues communicating with its own app while on site.
We have ruckus WiFi and go upload and download speeds.
The cat line has been tested with a fluke tester and it’s good.

Oddly enough i have anther site that has a unit connected back to the house that has to jump thru three switches (multiple buildings) to get from the gate back to the router and it works fine.

Overall i don’t have much faith in the product and tech support is hit or miss