GraphyGraphy Please note, that I have never used Sparkasse's payment app, but VR pay.
VR pay, at the time I used it, needed network and phone permission to work - and also google play installed in the same user profile. Without phone permission the VR pay app wouldn't even start properly, so this was mandatory. If you uninstalled or deactivated play services after adding cards in VR pay, it kept working for like 9 or 10 payments and then ceased to work until it found an active google play installation again. One time the cards disappeared or were greyed out, if I remember right.
I don't know, if Sparkasse's app works the same way. But it might well be. I never understood, why VR pay needed Google play and if IPC was possibly taking place. Since VR pay also had phone permission, I stopped using the VR pay app, because I had privacy concerns.