On vacation without Nuendo, but haven’t seen that yet.
Are you sure you haven’t got a level change post processing?
Clip level, fader or a compressed inserted with gain makeup?
You can always check the actual peak level of the clip. using the analytics tool
Just tested this here and both those plugins seem to work flawlessly. As Erik suggests… do you have some other fader or process on the track post processing which affects the level you see?
What version of Nuendo are you using? Mac or PC? What is the precise DOP plugin chain you are using and what are the settings?