AVM Repeater 1200 + current Snapshot

I have again a problem with AVM fritz1200 repeater (ipq40xx).
Is there anyone using this device with new version of Openwrt?

It worked fine for months with snapshot r24797-2fe8ecd880 (kernel 6.1) build 3 months ago 2024/01.
I've also tested today the release 23.05.3 (kernel 5.15), worked also.

Now i wanted to update with currrent snapshot but the device does then no longer respond and i have to recover it with avm tool and flash by bootloader again.
I've not console attached, when i open the device, the 230v power gets interrupted.

Any idea which change could break this device again? Perhaps kernel 6.6 changes for ipq40xx https://git.openwrt.org/?p=openwrt%2Fopenwrt.git&a=search&h=refs%2Fheads%2Fmaster&st=commit&s=ipq40xx ?
Or something like AVM Repeater 1200 + Openwrt 21.02 fixed by https://github.com/openwrt/openwrt/commit/f9d18281051c894eacd40f10c10b430c6c9082ad ?

Nobody except me uses a Repeater 1200 ?