I have the same problem with my VKB Gladiator Evo Joytick with the addon THQ throttle quadrant attached. Both are listed in MS2024 as VKBSim Gladiator Evo R THQ.
The First entry, which is the joystick device, has all flight controls mapped to it. It also has the throttle and propeller controls. This is because VKB allows for a certain number of axes per device, so I had to assign the mixture control axis to the second entry in the MS2024 control list.
In the second entry, all I mapped was the mixture control.
When making any flight at all, either free flight or missions or anything else, I always have to go back to settings, controls, and reset the second device back to the mixture control profile. It always resets the airplane profile, which contains the mixture bindings, to NONE. It will NOT stick, even if I set it as default.
Asobo, please fix this bug. In MSFS 2020, I also had two entries for this same joystick/throttle quadrant setup, but the settings stuck, like they should.
Thanks,
Bill