Sounds awfully like the rinse valve is opencirciut , these machines prefill via cold valve then sw to to hot valve then back and forth to make sure not over wash temp, during rinse they use the the other solenoid on the cold valve then for fab cond dispensing both the cold solenoids are energised, the pre wash light flashing is a fill problem.
update on this machine..recalled last night done diagnostic test no fault
found..changed cold inlet valves ( possible suggested fault) no joy
fill it must be pcb faulty. customer is buying new machine!!