I was in contact with Ancestry support throughout with these problems. I sent them screen shots of the multiple additions and error messages so that they had a full and complete picture of what was going on. 600 plus duplicated persons one day, all removed, and they were back the next day!!
Ancestry thanked me for the information and fullness of the report. I had exhausted all of their suggestions and proved the case. They informed me they had passed it to their developing team or technical people for further investigation. That was over a month ago and no response since!!
Frankly FTM was a complete waste of time. I this were a high street 'tangible' product, I would be demanding a refund.