Got my machine back from dealer a couple days ago after taking it in for this battery issue and it's annual service.
Problem was lose cables. When I most recently replaced battery back in October, I went to Lowe's and got some longer bolts to use to connect the cables to battery posts. Why? As anyone who has replaced the battery in the P5 knows, it is a pain in the ass to get the bolt through the cable eyelets and then get it to thread up into the battery terminal posts. So, I thought longer bolts would help make the process easier, which they did. I was able to find longer bolts which matched the threads and get em cinched em up tight, but they apparently did not stay tight, and according to the dealer's tech, that loose connection allowed the battery to drain. He recommended always using the bolts that come with the battery.
Fortunately, battery was still under warranty. Once they installed new battery, they checked electrical system for any parasitic draws and found none. Guess I gotta chalk this one up to bad luck. I now have a Honda OEM battery in the machine instead of a Huasa, because Huasa's were on backorder. Honestly, I'm glad as I had better luck with the original Honda OEM than I have with any of the Huasa's that have been in the machine. So, hopefully this problem is behind me.
I will add - service tech told me that battery quality, just like everything else, has been going down for several years, and it is therefore imperative to keep the batteries on a tender or some kind of trickle charger when the machines aren't being ridden.
I appreciate all the comments with suggestions trying to help. Thanks.