Originally Posted by BCRider

Instead of loctite I'd suggest you try greasing the threads of the bolt as well as the teeth of the ratcheting rack. ...
You'll also want to closely examine the teeth in the post now. Because they slipped a few times the crests of the teeth will be badly shaved away and each time this happened it makes it less likely that you will be able to make the post clamp well enough ever again. If it's done this a few times I'd say you're looking at a new post regardless of what you do with the screw.