[terry and jo]

While this is not a fix for the screws coming loose, it does work to stabilize the two brackets so one isn't trying to pull to one side due to the tension from the closures.

While I couldn't picture in my mind what some of the rest of you were doing in the earlier part of the thread, I turned to this idea just as a way to stop the flexing on the L-bracket.

Sorry that the one picture is fuzzy, but you can still get the idea of what I did. Basically, I used an all-thread bolt about 42" long and then used washers and nuts on both sides of each of the brackets. (I did have to drill the holes in the bracket though.)

With each "L" of the bracket directed towards the center of the door, the all-thread makes each one help stabilize the other against the forces of the closures wanting to skew either into or out from the center.