I had the same problem with the bolt in the spider assembly just spinning and not being able to remove the Lifter Assembly bottom to get access to the nut. I drilled out the bolt from the cap end. You could also cut the top off the bolt. The Lifter Assembly then slid off. It turns out that the nut was enclosed in a plastic retainer that wore to allow the nut to spin. There is a metal plate so you cannot just pull the Lifter Assembly off without removing the two bolts through the spider. In reassembly, I will use a new nut and bolt. I will have to use glue to keep the replacement nut from spinning.