Infinite bug - Custom controls conflicting

Playing on PC via Steam, using Xbox 360 controller

When I try to make a custom control scheme for Infinite, I am running into issues changing basically anything. All I want to do is use the Recon as a base and swap ‘switch grenade’ and ‘use equipment’. So I want LB to switch grenades, and left on the D-pad (which I’ll call D-left from here on) to switch equipment.

‘Descend/Trick’ in the vehicle controls will not allow me to have it on the same button as ‘switch grenades’. I can’t imagine why - if I’m flying an aircraft I don’t imagine I’ll need to switch grenades. As a result, I have to either use the Recon scheme or be unable to have that vehicle control.
The first time I tried to do that, it also unbound ‘equip slot 3’ and would not let me rebind to anything at all. I reset my controls to Recon and did the swap a second time, and now that one stayed put.
‘Equip frag grenades’ stayed on D-left both times.

I will say that I am IMMENSELY appreciative to finally have rebinding options for a controller. This should be a standard feature in games, and should have been for 15 years.