I removed the MMD to put on new blades. Now I am trying to reattach, and even with my old arthritic hands I managed to get the 2 side pins and the front bracket on but I cannot get the collar or coupler on the drive shaft back on the rear gear. I twisted and turned the bracket to even up with the hole, I pushed as hard as I could on the shaft housing where it rises towards the end. I cannot feel the click of the bearing coupler on the gear! What am I doing wrong?