Hi remarkable,
That's a rough one, especially after you've already tried all the usual fixes and still no luck. You've definitely done the right thing lodging a support ticket. With Banking Hub errors like that, there can be a few things going on behind the scenes, not always something you can fix from your end. Sometimes it just needs a bit of work on the backend, like running a script over the file or doing a file repair to get things talking nicely again. Good news is the support team will be able to dig into your file and sort that out for you.
Regards,
Sai