Not sure if this will be helpful or not. I went to a similar fault a few days ago. Sorry I’m not even sure what make of machine I looked at. But the fault sounds very similar. It was as though the mains was switching on and off as the machine was filling. Customer complained of machine switching itself on randomly.
A careful inspection of the plug which connects the mains to the control board at the front of the machine revealed what appeared to be a faulty plug. (Live would grip tag, neutral would not) I cut it off and replaced with separate tags and, fingers crossed, have heard nothing since.
Hope this helps
Graham