Stopping Indesit IWME147 mid cycle

Hi. We have an Indesit IWME147. Sometimes we will start a programme then realise we’ve left something out. We can stop the programme by holding the start button down for a few seconds, but the light stays on (not flashing) and the door remains locked, even if left for a good few minutes.

My understanding is that if you stop a programme the washing machine should drain and unlock within a few minutes (and I’m sure it’s done that previously). Are we doing something wrong or does this sound like a fault?

Thanks in advance for your help.