I had the exact same thing with the Quickbooks api recently. You cannot trust the responses or webhooks at all.

On create a user or invoice for example sometimes it will return an error, yet it actually created the entity. This means you have to check manually after creating everything to know if its created properly.

Then you have the issue that sometimes quickbooks takes a while to update, and locks the company file while it does some background magic. This means you cannot immediately do the existence check, and also sometimes the check errors or times out which essentially means you need to keep checking forever until you can properly reconcile your db against theirs. But with hundreds/thousands of transactions per minute this state is never reached. You perpetually live in a state of trying to catch up but never managing it.

When I brought it up with Quickbooks dev support their response was literally "Its your job to make sure things are created properly in our system".

How did we get to this place where we started putting up with systems that cannot ever be trusted?

That is the way enterprise software works as a system. It demands to be the central focus of everything. Workers want to route around these turbo productivity theater nonsense that could be replaced by a few K script that gates access to a text file and checks validity of appends. That can’t be allowed, so you need what is essentially whole poorly documented OSs to enable an economy of brokers to it, or the whole con would collapse.