The DJT module fits into 9XR like a silk glove. You should not feel any resistance or pressure while fitting it. The only force nescessary is when it is almost completely in and the plastic latches engage.
Check TX pins are absolutely in a straight line and all the same distance apart. If not straighten them until they are perfect.
Remove the cover from the module and ensure the female connector block that the pins insert into is vertical and thew base is flush against the board it is mounted on.
Insert the module while supporting the connector block with your thumb. It should slide smoothly onto the pins without being pushed up off the base. Any resistance means the pins are still mis-aligned.
Once module is safely in encapsulate connector block with epoxy or hot glue to ensure it won't move - ever - and then replace cover.