Has other sellers seen this type of behavior from lenders?

When they pay for the power bill, you just don't see that kind of behavior. 

I now find it difficult to trust a company with such questionable behavior moving forward.

If they were I report their behavior as a PM to the local realtor association because that level PM is not allowed.

Not saying that's the case, but there's something called 'Toxic Giving' which causes people to continue performing the same behavior to a point where they're absorbing resources that could have been used to help people who are truly in need.

In general, applicants are on their best behavior right before they sign.

Venmo and Zelle haven't had a huge crackdown on this kind of behavior yet, but they could at any time.

That's what happens when interest rates are at 8% and purchase price/gross yields haven't adjusted.The gross rental yield is only 9%, coupled with expenses it's less than the cost of financing - hence you earn yield by removing the cost of financing with cash.High rates encourage this kind of behavior (holding cash or using cash to cut interest expense). 

Friendly letters do not change behavior...Invoices do.

People who are lying to you (or scamming you) right from the start when they are (or at least should be) on their best behavior, are going to be more of the same if/when you rent to them.