BTT "Stealing" my shift key?

Hello all. Have an odd persistent bug that I've been able to trace back to involving BTT somehow. The Go/Nogo of the bug existing seems to be something in my current config, as disabling / uninstalling BTT fixes it. The bug affects my Mission Control Hotkeys, and a description of events follows.

Some background: For my mission control settings, I keep ⌘+M2 bound to Expose, and ⌘+⇧+M2 for App Expose. The ONLY features I have enabled in BTT are: Global bind of 3-finger swipe right activates application switcher, with "Use Special Application Switcher" turned on under "Predefined Action Settings", as recommended. Every other button and function I could find is explicitly disabled.

The bug goes like this: With BTT installed, the bug seems to be "masking" my left shift key from MacOS, as both configurations of the command (with and without the shift modifier) activate regular Expose, with app expose being effectively disabled. This problem seems to come and go somehow??? but is very, very consistent with BTT being active in the OS or not. I thought I had it licked before by activating "alternate CMD click mode" which seemed to fix it, but then the bug came back which prompted me to write here.

The story gets weirder though. First off, I tried changing the secondary modifier to anything but shift, like ctrl or opt. Nothing, exact same problem, didn't even phase it. Stranger still, after trying alternate binds I stumbled across a workaround for this, and I don't know what it means, but it has to be significant. By accident, I discovered that setting both regular expose, and app expose to the exact same keybind (⌘+M2) the bug actually fixes itself somehow????? With BTT active and that goofy keybind, complete functionality is restored. I get my expose with ⌘+M2, and I get app expose by adding my left shift modifier. Turning off BTT but leaving the goofy bind delivers the expected results, with MacOS not liking it, which in my mind confirms BTT as suspect #1.

Help? Ideas? This isn't gamebreaking as I've found a bootleg workaround, but it certainly is annoying. Thanks for the help!

macOS 11.2.3
BTT 3.560, lifetime license

if that information helps at all