Is it installed correctly? That is, is the closer installed in the right place on the door according to the instructions? Was the arm installed correctly, or was it installed in such a way as to get more power out of the closer than it was designed to have? These are the things I would check first.
Secondly, if there is this much force being exerted against this door, perhaps you might consider adding an overhead stop that will keep the force away from the closer.
It would be helpful to know whether these closers are installed on the push side or the pull side, but I think, because of the apparent force that is being exerted on the mounting screws, that they are probably mounted on the push side and are therefore in a parallel arm configuration. A parallel arm mount would be the only kind of mount that would apply a direct pull on the mounting screws.
If the closers are mounted in a parallel arm, when the arm is extended until it stops it will, in effect, pull on the closer body. Dorma's instruction sheet on this install actually has almost no words on it and does not say to what degree the door will open when this closer is mounted according to the instructions. It is unusual for mounting screws to pull out of the door or be sheared off. I think we can conclude that the door is being opened with sufficient force to 'bottom out' the arm such that it pulls very hard on the closer body, pulling out or shearing off the screws.