The LXD 75/55 series is famous for broken gearbox covers. The screw pockets break off of the plastic covers. The repair is actually simple. Remove all of the remaining pockets with wire cutters or a dremel, and sand with 320 grit sand paper. In the photo you can see I have removed two of the four pockets to show before and after. Print 2 pieces for each gearbox. Attach them to the mount with screws and test fit the cover. If it doesn't fit try rotating the mounts 180 degrees. You can see the screw holes are offset. Add super glue to the cover and the new pocket mount and press the gearbox half into place. Make sure cover is not contacting the drive gears. Once glue as started to set, wait 4 hours before screwing the other half of the gearbox cover into place. For the azimuth knob, print the part and press it on to an 8mm x 1.25 socket cap bolt (35mm length). Be sure align the hex socket with the hexagon inside the knob. If you are printing ABS, you should scale to 103% to allow for shrinkage.