I found at least 3 bugs in their systems.
I had more than $6 credits in S&S account and $4.5 in Shell account, linked to each other. Bought fuel from S&S station on 10/29, only $1.5 discount applied. 3 bugs as follows:
1. The total discount should cover the gas price, but only $1.5 discount applied.
2. In S&S account, 1500 points deducted from points with late Oct. expiration date rather than points with 10/3 expiration date.
3. Both S&S account and FuelReward account lost 1500 points after the transaction. So they deducted 3000 points total for $1.5 discount.
Please be aware of the bugs, and share your experience. In particular, is there similar bugs at Shell stations?