I just reproduced it easily by making two parallel tracks at 0.2mm one from each other.
Now if I try to increase the size of the track "pad 1", i.e. to move the bottom right end horizontally towards the right, I will get an error: each time I click again to finish the move, I get "err 16 or17: two tracks end too close"... except for some specific distances! E.g. dx += 0.5mm will be refused, but dx += 0.925mm will be accepted.
I guess that I am having the same problem.
I just reproduced it easily by making two parallel tracks at 0.2mm one from each other.
Now if I try to increase the size of the track "pad 1", i.e. to move the bottom right end horizontally towards the right, I will get an error: each time I click again to finish the move, I get "err 16 or17: two tracks end too close"... except for some specific distances! E.g. dx += 0.5mm will be refused, but dx += 0.925mm will be accepted.
Track width: 0.25mm
Grid: 0.025mm
Clearance: 0.2mm