TE/TC 250i backfire on shutdown

Since new my 2020 will sometimes, apparently randomly “pop” a little when I hit a red off button. No biggie. But today on one occasion she did it and shortly after when I tried to start it again, no go. After a few stabs she got going again but I expected a decent push back to the Ute, such was the uncharacteristic time it took to eventually start. After this episode all was good with about 5 stop and starts behaving perfectly during the rest of the solo ride. Anyone else had this issue? Could it be the sign of a bigger problem?
It was a bit warmer today, about 30.