Unavoidable collision while measuring curve

[[Da...]]

Its mutch easier to understand how this clearances work with 20 years old Mcosmos than novadays calypso
I did it few times but its just not work today
Need to measure this little part marked with orange on first photo, also have manual points but they work only before measurement
it starts fine but after measurement its going little up as i inderstand clearance but later it moves ... like acording to this green arrow whatever it is, because i do not know
i tryed diferend seting with this clearance set to 0 and not at all but i do not see diference

any ideas ?

edit:
i did new curve and changed direction to scan from differend side and now it works fine without colisions and manual points, but anyway i'm still interested how to fix it because sometimes may be not be poseable to from both sides