I'm not sure why you're able to control the flaps with a key binding that's been removed. To be thorough, try renaming the fsx.cfg, Prepar3D.cfg, dll.xml, and exe.xml files in the %appdata%\Microsoft\FSX, %appdata%\Microsoft\FSX-SE, %appdata%\LockheedMartin\Prepar3D, and/or %appdata%\Lockheed Martin\Prepar3D v2 folder(s), depending on which simulator you're using, as well as renaming the Standard.XML in the %appdata%\Microsoft\FSX\Controls folder (or the Controls folder for whichever respective simulator you're using). If you've done this correctly there should be no third party addons launched alongside the simulator, and the control mappings should be set back to default.
After doing the above, go for a test flight in the FSX Blue Angels Hornet and when loading the aircraft, only allow the HornetFCS gauge to run (disallow all other gauges for the time being). If the flaps work
as described by Jimi in this post, then you can begin reintroducing addons, preferably one by one, testing the Hornet after each addon.