First of all: great work on the journey planner. I use it often and find it consistently produces enjoyable routes.
I've been noticing some odd behaviour with the "Click map to add more points" feature. I've been able to reproduce it with the following steps:-
1) Click on the map to add a start point
2) Click elsewhere on the map to add an end point
3) Check the "Click map to add more points" box
4) Click on the map to add a new endpoint
5) Drag the endpoint to a new location
If you now click near the end point (say within 100m or so) it will not add a new point. However, if you click a point which is closer to the start point than the end point then it will move the start point instead. Once the start point is moving it will move that so long as the point you click is either closer to the start point than the endpoint or very close to the endpoint.
I've been able to reproduce this in Firefox 92 and Chrome 93