I have not looked at a 115 before so can not say as to how it adjusts but something must be moving I have not adjusted the deck on my 180 in 25 years.
You are using the correct method to adjust it so look for what is changing.
As the dealer not getting it right that don't surprise me this spring I bought a new ez trak from Mutton in Ft Wayne this is a big place they sell one hell of a lot of JD'S and when I got it home the deck was not adjusted right,, I had to do it myself.
Makes me wonder what it would be like if I hired them to do technical work
I agree. I called the local JD dealer and spoke with the parts and service guys to ask where all the grease zerts were. They both said they had no idea without looking at a manual. You would think that a couple guys who work on mostly the same equipment day in and day out would have an idea where to look for zerts. Geez.