There is currently a bug in Microsoft Flight Simulator affecting users using multi-engine throttle quadrants (such as the Thrustmaster TCA). If you have multiple engines assigned to a single physical axis and have both the "TOGGLE THROTTLE REVERSE THRUST" and "DECREASE THROTTLE" binds mapped to multiple buttons, one of your throttle levers may stop responding to movement.
Identifying if you are affected by this issue
You are likely experiencing this issue if your control settings meet both of the following conditions:
- Throttle 1+2 are assigned to the left throttle lever, and Throttle 3+4 are assigned to the right throttle lever (Image 1).
- You have both or either the "TOGGLE THROTTLE REVERSE THRUST" and "DECREASE THROTTLE" binds set to two different buttons which must be activated at the same time (Image 2).

Resolving the issue
Because in the above example the "TOGGLE THROTTLE REVERSE THRUST" and "DECREASE THROTTLE" key binds are set to two different keys, which both have to be activated at the same time, this bug will appear. To resolve the issue, simply set the "TOGGLE THROTTLE REVERSE THRUST" and "DECREASE THROTTLE" keybinds to one single key. For the example above, this would mean setting it to only be activated upon one leaver/detent being activated, but both leavers and detents can still be physically moved.