Experienced CNC prototype machinist here. However, I haven't run anything newer than 2008 until now.
Ive got a 2020 DNM 5700 and the process for touching off tools that Ive been using on my 18i is giving me inconsistent results.

Normally, I make sure that my Pos Rel Z value is zero at Z ref return. Then bring tool to tool ref plane, Z, Input C.
On this machine, the Z Ref position is above the tool change position and when you do a tool change the Pos Rel Z position changes in the control. If I reset this to Zero after every tool change, it gives me the right value but this cant be the way.

This machine has a Fanuc I-series control. I think its the Oi-F Plus with a Doosan skin on it.