Interesting, this is the same issue I had. This was around 3 years ago, though.
Have you tried spinning up your own Postgres instance to see if the same thing happens? It might help to be able to show them that you’re able to resolve it when you don’t use their DB.
We're using the MySQL product, but it's interesting the exact same problem is happening on multiple products under the umbrella. It's not my job to deeply diagnose their issues, and their support wasn't able to even comprehend what I was asking in very plain English. What I could have gained in offloading the maintenance to them was lost in hours wasted so far, and I'm probably better off bankrupting the experiment. When I say small, I really mean it: less than 10k rows in the database. Queries only interacting with primary IDs, etc. It's mind boggling.
Have you tried spinning up your own Postgres instance to see if the same thing happens? It might help to be able to show them that you’re able to resolve it when you don’t use their DB.