Ah, I can see the complication.
To be fair though, if I was in your shoes I’d be getting a little frustrated too. It’s not you who is dragging their heels... That said, I don’t recall you ever being disrespectful.
In my experience, aggression in these circumstances is a sign of deflection. There may be genuine reasons and complications for sure, but clear and honest communication makes sure everyone knows the position. At the end of the day, YOU are the customer after all.
Let’s just hope it’s gets sorted soon and both of you can move on as when it’s all said and done, you just want your car back.