I have a corded Mighty Mouse, so no batteries. I was able to disassemble it and cleaned up the ball rollers. The side buttons are attached to the main housing and I am having trouble getting them to engage the bottom cover (figures 5 & 6.). I have not found a way to insert them from the outside in main housing. They don’t seem to be able to back out of the housing enough to allow the base to properly set in place. Suggestions?