Be careful sending the German made Sigs in for service. You may loose your better parts tool steel sear to mim parts. The German made sigs have better internals in my book. Check to see if you have the plastic or metal main spring housing. Should have the metal one if it's 100% German. Sometimes these get changed out for the plastic one for it's easier to service and lightens the trigger some used is the QST. You say the trigger is light in SA. Have you measured the pull. It could be just that it requires very little movement (rearward travel) to release the hammer. This is a easy fix that only take s few wipes on a stone to increase sear/hammer engagement. Most of the German Sigs I've checked have ~ 3lb SA where the DA is around 10lbs.
If it has the quick reset the internals have already been changed.