Ongoing (battery?) issues with Aqara WXKG15LM

I really like how the Aqara WXKG15LM (battery powered double rocker wall switch) looks and costs. I am however facing ongoing issues with them. I have 3 wall switches and all 3 are having battery issues. Most of them times the wall switches even do not operate when I put new batteries in them (tried 2 different brands and multiple batteries). Yesterday I managed to bring 1 wall switch to live and paired it to Zigbee2MQTT, but this morning the wall switch is already fully dead.

If I test the batteries with a battery tester like the one below then batteries appear to be full.

Are other people experiencing the same erratic behavior?

Are you sure it’s the batteries? How many routers do you have near the switches?

Can you show us a map of your Zigbee network?

Well… On the switch there is a small, blue light that should blink when a button is pushed. Also this light doesn’t go on when I push the button. On the other hand: I canno imagine me receiving 3 faulty switches (or receiving 25 faulty batteries from 2 vendors).

My Zigbee network is very stable with plenty of routers (6 within 4 meters direct line of sight to the switches). Find below a screenshow of my map (Aqara switch encircled in red)