Hi Petr, this one will be a bit difficult to fix up.

For arc or circle tangent, there are usually multiple possible solutions of the given radius - the points that you pick are used as seed points that then converge on a solution local to those points.

But when you pick on the quadrants in the case you show, that is the exact boundary between the case for getting the small arc like you show versus getting the larger arc like this:


Clicking exactly on the boundary area tends to confuse things, you need to pick more on one side of the "hump" or the other to disambiguate which solution you prefer.

It would be possible for me to make this situation work better, but it will take a fair amount of work so I will probably procrastinate on that for quite a while. But thanks for reporting it though.

- Michael