If you are having hang fires, The hang fires are caused by your "reduced loads" not anything to do with the rifle and they can be very dangerous. No doubt you are below published minimums which is a NO NO. Not just because you dont know when they'll go boom but dangerous overpressure is a possibility.
It's a physics thing that few fully understand but severe over pressure can result from such loads. That's why every single loading manual that I have seen specifically warns against going above or below published minimums.
If you want to reduce loads the best and safest way I'm aware of to do so is using H4895 and Hodgdons reduced load data using their 60% of max formula. https://imrpowder.com/wp-content/upl...ifle-loads.pdf You can also call Hodgdon Powder Company if additional information is needed, 913-362-9455.

As far as the trigger goes, From what you describe, pure speculation but it sounds to me like the first guy may have tried to polish sear engagement surfaces and rounded em off or changed the angle. Sounds like the guys at Timney may have been close and just needed to back off the sear a hair and/or may not have realized if (pure speculation) someone had monkeyed with the sear surface. Sounds like they and the third guy may have the sear adjustment set a little light and if so they dont stand a chance of getting it right the surfaces are as I speculate and may be "boogered" up. Savage trigger jobs are fairly simple straightforward and safe for someone with a basic mechanical aptitude and understanding of how they work.
A trigger spring that's adjusted without an arch in it can also result in an improper set of the sear and slam fires and erratic cocking. If no one messed with the sear surface then that may very well be the problem. I always replace the trigger spring with a lighter one when doing a trigger job but I also always make sure there is sufficient tension and a slight arch in the new spring as well. Just reducing tension by setting the old spring flat is a recipe for disaster.

The rifle wont stay cocked if the trigger and sear are not making contact as the bolt stop sear combo is what holds it in the cocked position. If the bolt handle is up, that's not cocked. It cocks on closing with the trigger pushed forward by the spring at which point the sear should set against the trigger.

Good luck and above all be safe