As expected the lenses of the laser modules did not stay in place. To focus the lasers to the surface of the to be cut material the lens holders need to be screwed out as much as possible. This allows rocking the lenses back and forth. To fix that I now glued them in place with medium strength bolt adhesive I had at hand. Weak adhesive would probably be better as one side of the thread is only plastic. But any other glue would probably also do.
Other than the loose lenses the overall design has worked very well. Many users have praised the new targeting laser. There is really nothing left to do so I declare the project done.