GBIT double charge on destination card

Did a GBIT (Go Back In Time) yesterday from Card A to Card B. Both credit cards. Amount=£721.82.

When i attempted it, a message came up:

Go back in time unsuccessful

The payment card for this purchase has not been charged. You can try again or contact us and we’ll be able to help.

I attempted it again, and this time it was successful.

When I checked the card B account using app, it had reduced my available balance by £1443.64 (£721.82x2). So for example, if my available balance before carrying out the GBIT was £2000.00, after carrying it out it has become £556.36, when actually it should be £1278.18.

I checked the app again today, and my available balance is still £556.36. Nothing happened because I’m still within my credit limit, but I wonder what would have happened if the available balance went in to negative because of this.

Perhaps when the transaction eventually show on recent transactions the available balance will correct itself?

Anyway, I figured I’d put a word of warning for others, especially if you happen to see the '‘Go back in time unsuccessful.…’ message in the first instance, maybe worth checking the destination card account to see if it’s reduced your available balance before attempting GBIT again. Because if you are close to your credit limit, and you re-attempt GBIT and it goes through, you may be slapped with overlimit charges etc.

By the way, if we were to incur an overlimit fee by the credit card issuer due to a double charge (while doing a GBIT or making a purchase through Curve card and it’s clearly a Curve card issue), does Curve refund the underlying card issuer’s overlimit fee?