Got a question about A Toro Rider. When I go to put the blades back on it (2) one of the shafts the screw goes into doesn't screw down tightly. It's stripped, it'll grab some but then when I go too tightly it just loosens up again. I believe it's grabbing enough to hold the blade in place but probably barely that. What's the fix for this? Does the "Shaft" have to be replaced? I only have basic mechanical knowledge (and tools for that matter.) Is this something I should attempt myself or have a shop tackle it? Thanks!!