Isar HE 35 again problem?

Hi
Last winter (thankd to this forum) I did replace diverter valve, temp gauge and water pump and spring comes so all went perfect. Now new winter approach and ....guess what...new problems. Will try to describe the "ilness" as much as I can.

Boiler is heating much oftrn than use to hot water "d" sometimes after longer time like 5 min it is only burner control blinking and burner does not works. It blokes from time to tme to switch CH. Now, another issue, when I switch CH boiler shows "c" but burner control blinking and burner is not working. After longer time (or when I do switch off the boiler) starts working but also without getting the proper temp again switches off the burner and light is blinking "c" on the display.

I need HELP as have no clue what may be now?

Thanks in advance.