Hi Matt,
Digipoints are the intermediate points, that you may also call vertices, which define the shape of the branch.
When you edit a branch on the map, all these digipoints appear, and you can move them graphically. So I suppose that the solution to your problem is to move a digipoint close the mentioned chainage, and you'll probably see that you had 2 of them superimposed, which may be troublesome.
If you have two points at the same location, you can simply delete one of them.
Best regards,
Mathieu