Hi Peer, a couple of things that might help the tangent solver for this case are first to place a point object (Draw curve > More > Point) at the endpoint and then slide the line down a little so that it can converge onto that point from either side.

The other thing that could influence it would be to hide the line before picking the 3rd point because it's probably trying to do a "tangent to 3 curves" operation since the through point is on that line.

To hide the line, select it before drawing the circle and then push Edit > Hide before your 3rd pick.

It seems like there could be a geometric solution since the circle's center point will be located on a perpendicular line off the end. So if a second constraint can be determined they could be intersected to get the solution.

- Michael