I bought a Sanus wall mount and had no issues getting the first three screws into the studs. This mount uses hex screws. Screw #4 was about a half inch from pay dirt when the screw got stripped. I was able to back the screw out and try a lag screw in its place. Either I have horrible luck or there's a knot in the stud. The lag screw broke in half, leaving the remainder of the screw inside the stud. I'm going to try extracting the screw but don't know if I'll be successful. With that in mind, I'm trying to come up with other solutions to shore this thing up just in case.
Because the mount is secure with three out of four screws in place, I don't want to back these things out so I can try a toggle solution from the front. I'm concerned about stripping the other hex screws and causing more problems. Most reasonable solutions won't work because the mount is already attached to the wall. I am also limited by the size of the cut outs on the mount, restricting what I can put into the wall from the front. I do have some limited access to the back of the wall. What would be a recommended way to use some sort of toggle bolt or other solution to anchor this thing to the wall? My first thought was two toggle bolts on either side of the stud. I'm not sure if a conventional toggle bolt is adequate in this case.