I had the supplier come out to look at mine 3 times for a very similar issue to yours.
One time, they wedged a block of wood in the bottom and pushed the top of the door - it flexed back in and aligned much better.
The second time, they ‘adjusted’ the bit which the locks connect into (no idea what this part is called, it’s the bit on the frame not the door) by putting a plastic spacer behind it. This did allow the dowel like latches to pull the door in tighter reducing the gap.
I think the final time was a bit of token fannying about with it before they said that it was as good as it could get.
I did get a partial refund, but I have come to the conclusion that they are just never going to be airtight. Although I will say that the other set without the pedestrian door is much better.