that’s an odd one
normally when a programme finishes then the timer goes to zero and you cant set another programme till you move the programme knob to reset and then press start
cant think what it could be other then the timer but would like to prove it and see it happening if it was my job. Is it repeating same prog or does it do another one
if it was the old mechanical timers then it was a fault I have seen. normally caused by a blocked pressure chamber
Dave