Update…
Thanks to everyone who commented and made suggestions. I found out there was more to my issue. Upon unscrewing the tree and removing it to slide a washer under the disc part of the tree, I discovered a hole that looked to have been drilled by a three year old. A small piece of wood also came out of the hole. It appears that the hole for the tree was poorly drilled and then the person assembling the instrument tried to correct by just putting small sliver of wood in without gluing it. The tree was doomed to fail under string tension. Mind you, this is on a brand new Fender Am Pro II bass! Unfortunately, I’m leaving for a week long gig and don’t have time to send it back. I added some small slivers of wood with wood glue and let it sit overnight. This morning I carefully shaved the wood insert down to nearly flush with the headstock and sanded it very gingerly. I re-drilled the hole, and tried the original screw. It wouldn’t bite. Grrrrr… I added a bit more wood and found a screw that was just a hair wider and longer than the original that I’m happy to say it’s now holding. All of that on a brand new, American made, $1,800 instrument! Needless to say, I emailed Fender about my frustration but the main thing is my instrument is functioning well and I’m ready for the week.
Thanks again, everyone!