Had this issue on a 2-week stint I just had in Shanghai:

Some restaurants, if you have enough balance on your Alipay, will pull from balance no matter what, even if they otherwise accept the attached foreign card (it seems like there is a way for them to ignore your preferred payment order?). Had this happen at Blarney Stone and one other place (the name escapes me for now).

For reference, my payment order is:
1) Visa Card
2) Master Card
3) Balance (with my intent to use it for TakeOut and minor charges where cards aren't accepted)

Typically, you can see it "trying" to go through the payment order before relenting to balance, however in these cases I scanned and it immediately came off of balance. This only happened when the balance was high enough to cover the whole bill, whenever the balance was low, it acted properly and went through the preferred payment order.