Are you using P3D 4.2 ? If yes, this has been already explained countless of time on the forum, and it's the very well known menu bug introduced in 4.2, which results in menus options being auto-selected, if you (or another addon), use the numeric keys on the keyboard.
If this is the case, your only option (while waiting a fix from LM), is to disable every usage of the numeric keys on the main keyboard from every addon that might use it.