RAK4631 not responding via serial, not showing up in bt. Erase fw and current fw flashing seem to work. Any ideas?

+++ UPDATE +++ Using 2.5.20 ("alpha") works! Thanks a lot! +++ +++

Hi, I've bought a meshtastic starter kit, hooked it up to a big, quite full lipo battery and everything worked for one day. I chatted with other meshtastic users in long fast, everything was fine.

After returning from work the blue led was off and I couldn't connect via bluetooth anymore.

I pushed reset and the green led started blinking every some seconds for one second (later turned out this were booting attempts). Still could not connect.

Connected it via USB to a windows PC, went to client.meshtastic.org. Seeing that the device appears and dissappears every some seconds, realizing it's in a boot loop.

Entering dfu mode (so that it shows up as a drive in the windows file manager), checking if version is 6.x or 7.x, copying the right factory erase fw file onto it - seems to work.

Dfu again, copying the current beta fw.

Kinda boots, green led stays on. Keeps showing as a serial device. Still not in bluetooth (2 different android phones).

Client.meshtastic.org shows device in serial list. But I can't see any config, can't see device name.

Install python for cli connection. meshtastic --noproto finds device, connects, but shows no messages from device.

The same when powered only by USB, only by battery or both.

Don't know, what to do. Any ideas other than abandoning it?