I'd be tempted to let a local electronic repair place replace the pot on the A5 card.

As long as the printed circuit board isn't damaged, it should be fairly simple to replace the pot for someone who is good with a soldering iron.

You wont be able to see the rear of the circuit board unless you dismantle the card BUT that would break the anti tamper warranty stickers!

As for a new board, there still available new from BT Toyota.

Looks like whoever replaced the card last time was a little heavy handed adjusting the pot!

Its been at least 4 years since I last replaced one of these cards, very rarely they go wrong.