I have a Dornbracht thermostat module, and recently noticed crosswater (hot going into cold) after my block of flats shut down mains to repair the boiler.

Think they have not flushed the pipes, probably debris stuck in check valves on the Thermostatic module.

I can't seem to find any maintenance docs for Dornbracht, but I do have the original installation manual.

Do I disassemble and pull the cartridge and clean following the reverse order of the manual? Not too sure if I can disassemble and clean check valve?

Any suggestions?