Does ACH have problems with actors making unapproved transactions from other's accounts?
Edit:
To answer the other part of your question, originating financial institution (ODFI) can issue a chargeback up to 60 days after the money was sent. Unlike credit cards, there isn't a process for the merchant/service provider to refute the dispute.
So, the bank account owner can dispute the ACH transfer with their bank a month and a half later and it pretty much assured that they'll get their money back. Their bank isn't going to fight their own customer for it.
If this is a merchant account which it needs to be if you're pulling from other ppl's accounts then yes. Hence the very strict consent rules. At the end of the day there's no guarantee of course but if it comes to litigation a recorded message with a verbal approval might tip the scale in your favor. Most merchants don't bother of course and just write this off as a cost of doing business and recoup the funds by factoring fraud costs into their prices.
Which is why if you pay your credit card statement by phone for example, you'll hear the service rep read the consent form for you to say 'yes' once they are done before they can withdraw the funds.