Copy function sometimes won't work

When I copy a line on the surface by clicking the line, pressing Ctrl, entering a dimension and pressing enter, it doesn’t copy the line for me, so I have to use the guide lines. But if I do the same thing with another line in the same group, it works.

you do have the move tool active?, as control is a modifier of both move and rotation
maybe best to upload the example.

I noticed that this line is the problem, if I delete it, the copy function works.