Shelly 3EM also disconnects with other shelly devices

I have newly installed 3EM shells in the switchboard. We have another 10 shelly1 and 2 shelly motion (version 1 and 2) in our household. All are set to unicast and static IP address. All shells have a dedicated 2.4 GHz network.

I measure the power supply and 2 other circuits (through the contactor). I control 2 circuit breakers at the same time, which was probably a mistake.
When I turn on the computer on the controlled circuit, all the shells disconnect and Shelly 3EM needs to be added again through the application. But other shells don’t connect right away. Could it be related to that controlled circuit? At the same time, the 3EM shelly emits an audible sound (still the same). It is normal?

Is it a wiring problem (an electrician did it) / wifi / harware / software? I note that the problem does not occur if a PC is not connected to the controlled circuit (approx. 100W consumption). The control can be turned on, but there must not be a higher consumption.

Can you draw a diagram?

I’m having a hard time following your description.