Need a Pro: Intermittent No Crank 2008 Volvo S80 3.2 fwd

[LanceALatte]

Hi all. I have a 2008 Volvo S80 3.2 front wheel drive automatic. For the past 2 weeks I will get a no crank/no start about 80% of the time while attempting to start the car without disconnecting the positive battery terminal from the battery and reconnecting. In the cabin, all lights, audible reminders, buttons and features are working as they should with no dimming. I put a new battery with correct specs in. I checked to make sure there were no loose connections or corrosion at the starter and solenoid. I checked the starter relay and reseated it in the fuse box (it either works or it doesn't I believe). I cut the positive wire from the starter by the battery terminal and got rid of the crimped terminal fuse and installed a copper lug with no fuse for a temporary fix. There are pictures of the OEM lug with a non-reusable cover for crimped terminal wire, and the aftermarket lug I replaced it with a temporary fix in mind (something a few people recommended to fix their cars with the same problem. It didn't help). Rarely a "Steering Lock!" or "Immobilizer try again" or "Shift to P" message will appear after attempting to start, but it really isn't often. It is reliable in the aspect that I can unhook the positive terminal and reattach and it will start after electronics come back on. I am really at a loss as to what it could be, and I've spent too much time with the issue. Has anyone had a similar experience with a fix?