I saved several gift cards as payment methods in the Migros app at SubitoGo so that I could use them to pay for my purchases. Wrong! When I tried to pay with the gift cards several times and one of them didn't have enough credit, the app froze so badly that even customer service couldn't complete the purchase correctly.

I had to close the app completely and then complete the purchase at a checkout.
Is there a trick I can use to use up the credit on my various gift cards without crashing the SubitoGo or customer service cash registers? It can't be that I now have to make purchases in such a way that I reach the exact amount on the gift card.