Pi-Hole as docker container on Pi 5 with NVME SSH crashes every day

It looks since last update almost every day I get the issue that I can't anymore SSH to my Pi 5. The only way to be able to connect again is a power off/on. Then I can ssh again and if I open the Pi-Hole UI I can see that since it crashed there was nothing recorded. The charts show no data till my power on/off.
The Pi-Hole is running as a docker container. There is also a portainer and wireguard running as docker container.
If I'm in this crash state ping to the Pi-5 is working.
Also VPN connections to the wireguard are still working.
But connections to Pi-Hole UI and also Portainer UI aren't working.
Pi-Hole UI shows instead this error.
Error 500: Internal Server Error
Error: Cannot open script file /var/www/html/admin/login.lp

What I already tried.
I have run apt-get update and upgrade.
I have stopped the Pi-Hole container and since then it diden't happened again (2 days).
Checked with if there are voltage messages in the boot journal, but there is nothing.
sudo journalctl --no-hostname --full --boot -2|grep -I volt

Details about my system:
I'm running a Pi 5 with NVME SSD.
Linux Raspberry5 6.12.25+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.12.25-1+rpt1 (2025-04-30) aarch64
Portainer version 2.27.6 LTS
Docker version 28.1.1, build 4eba377

Does somebody have an idea what the issue could be?
Where I should search next?
Before it started to happen, beginning of March, this configuration was running without issues.

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