I love playing Internet Expert on these things.
My bet is the lead sled is creating as many problems as it solves. I had one and ended up giving it away, especially since the recoil on the 375 isn’t that bad to me. I’m usually good for around 50 rounds off the bench with my 8.5# scoped Montana 99.
What I found with the lead sled was that it changed how I could hold the rifle and how to try and line my eye up with the scope. It was enough that not only did my groups open up significantly my point of aim/impact also changed. It was massively frustrating.
I also found the sling studs were causing a problem shooting off bags And
touching the bags under recoil - so off they came. That helped a LOT.
The third thing I changed was my left hand (I’m a right handed shooter) under the forestock. I found that my left hand would throw the point of aim on the bench. So, for bench shooting my left hand is isolated away from the gun.
By focusing on my technique and getting the basics down my groups regularly shrank to 3/4” or better.
Have you tried letting someone else shoot it? How have they done?