Dresden Elektronik scene switch not resetting

I’ve recently had issues with my Zigbee network in Deconz-Phoscon. Those have been resolved, with the help of this forum. However I now have to re-add my Zigbee devices. I cannot get the Dresden-Elektronik Scene Switch to reset for repairing. I made it work once in Phoscon, but when I remove it from Phoscon and try to add it to Zigbee2MQTT or ZHA it doesn’t reset. It gets stuck in the ‘Entering configuration menu’ (pressing two corners of the switch), or doesn’t even do that. When trying the reset (pressing all 4 corners) it does not reach the continuesly on red LED , so it does not reset the switch.
Is this a software firmware issue or might the actual hardware of the switch be broken? Is there something I can do to resolve this issue? What steps can I take to resolve the issue other than the ones described?

p.s. I’ve bought a new CR2450N battery (Renata), tested it in battery tester , and put it in the switch the right way up.