Default keybinds cannot be cleared

I play on PC, and I cannot clear the default keybinds for anything.  When you click on a keybind that you want to edit, it says 'Press ESC to clear...'  Well, I press and hold ESC and all that happens is the window closes.  This is an issue, when I use both of the thumb buttons on my mouse (M4+M5) for my secondary and melee actions.  When I bind those two, the game will not let me clear the existing keybinds, which are associated with Gadgets 3 and 4.  

Well, a way around this would be to just throw all the keybinds that are problematic onto a mouse button that I don't use, of which there are a couple; but the game doesn't even recognize any mouse inputs besides the two typical thumb buttons.  I can change the keybinds, but the only ones that I can clear are the ones that were blank to begin with.  

I've got decades of FPS muscle memory that BF6 is throwing out the window...