I came back to mystery shopping about a decade and a half ago. I have opened (and closed) many bank accounts during that time and opened (and closed) many credit cards during that time that were done as shops. I have not seen the situations you describe nor heard about them from other shoppers.
The situations I have seen are: a scheduler candidate being given access to the database and making an unauthorized copy of it for ???; companies having their databases hacked; companies going out of business and their computers being seized and sent to auction for unpaid debts (presumably those computers not having been erased); a scheduler turning over her database of shopper email addresses (probably just sold us) to someone who solicited us for face creams and similar junk.
During that decade and a half one of my credit card numbers was used in rapid succession for three purchases at local drugstores and at a casino on the other side of the country. The credit card company notified me promptly and took care of all four uses. My card was likely skimmed and the data sold. The card company sent me a new card/number.
There have been two attempts to open new credit cards in my name, both of which were thwarted.
I had the direct deposit of someone else thrown into a checking account I opened on a shop that I could not get rid of to close the account before it started collecting fees. I could see who the money belonged to but the research on the web could not yet get me to get her phone number and call her unlisted phone number. I did try to contact her through Facebook with no response and eventually went to the Federal Reserve with a complaint, which led to the money being removed from my account to a 'suspense account' so I could close my account. Her account number varied from mine in that two of the digits were reversed. Even at the local bank level they could see her account, but could not fix it without a direct request from her and they would not contact her to tell her.
My best guess is that you have a coincidence with two inept banks.