Potential Walmart Manipulation of Gas Selection at the Pump - Has anyone else experienced this?

I just recently started trying to use the Walmart station and App feature to begin getting 3 cents off the price of gas when using the Walmart app at the pump. Below is the scenario that occurred - I am wondering if it is an exception that has only happened at my Walmart gas station or if it is a bigger manipulation issue Walmart has designed into their pumping station equipment. When you scan the QR Walmart code on your phone to obtain the 3 cent savings, the pump instructs you to take the nozzle out and THEN select the gas grade. I followed the directions - I took out nozzle and inserted in the tank and then pushed the lowest gas grade. I then proceeded to pump the gas. After I completed filling tank, the pump showed that I instead of pumping the lower grade at $2.96 cents, I was charged for Premium fuel at $3.17 per gallon. I went to the manager, she said there are a lot of customers that experience this issue. What did I do wrong? When I took the nozzle out of the holder - I “should” have stood there and waited for the app to catch up and then selected the gas before turning and placing my nozzle in the van gas tank opening. She stated that the gas grade selection buttons are so sensitive, that simply brushing the gas hose against the Premium gas selection button made the selection for me. She stated that you can’t change the selection once it is initiated, so pressing my lower grade button does not change the initial selection of Premium gas. If I had even noticed the issue the only way to correct is to void the process and start over. Has anyone else experienced this with using the Walmart app at their Walmart gas station? I have never experienced this type of issue at any station pump.