I know that this is not a helpdesk 
Been using HA for some ages already (from version 0.50 I guess) 
Now something strange happened:
updating HAOS from 2025.4.0 to 2025.4.2 I lost a bunch of custom components but due to missing Python modules:
Problem is that restoring backup does not work, nor the fresh install when trying to apply ANY backup, even from 2023.5 (eldest I already deleted). When applying backup during onboarding throws an Unknown error
System was the latest before update, backup was OK (nothing bad in logs).
I know that my system is lowly( RPI 4 with 2GB and 120GB SSD) but so far it acted flawlessly with monthly updates and betas.
Where is the (simple I believe) catch?
Solution:
trying all kinds of restore from various backups and fresh installs I at last decided to use solution from days I was running HA core install:
via CLI issued
ha core update --version 2025.4.0 --backup
to issue a core downgrade… and all runs as before.
What was the problem with 2025.4.2 update and generated backup-IDK
My guess is that update messed up some dependencies in core and restoring did not repair them?
So for now not couraged to try 2025.4.2 again…
Best, JR