The SP mower has a feature to prevent rollback. It's a design feature to prevent rollback in case you are stopping on a hill, for example. The thing is meant to be pushed forward just a step or 2 to release the rollback lock. Another way to defeat it is to release the SP lever a few steps before you plan to stop. As far as the trailing shield. Any mower I've ever had, including my 21" EGO, has always had the trailing shield sort of go under the mower when backing up. It's going to happen just because of friction between the shield and whatever the shield is laying on. This is totally normal.