If you have to start the FSDT Updater before start FSX, it seems to indicate something is setting a wrong "Compatibility" setting in FSX, one that shouldn't be applied, and the FSDT Live Updater fixes it.
Sometimes, those wrong registry settings are set by legacy add-ons not fully compatible with Windows 10, so they set to run in a Compatibility mode when they start together with the sim. In other cases, Windows itself is setting some compatibility flags in the registry, usually after a crash ( even a crash on exit ), because it assumed the program required it ( because it crashed ), but in fact it didn't, and our software works perfectly fine with no Compatibility options in all default settings. The FSDT Live Updater restores them as they should be.
