While debugging the practise I realised that sometimes the vector didnt represent itself good.
When the first part is 0, it is not accurate with the second part symbol. I include 2 photos
On the first one, the red vector should point to the right, but it does to the left. Including a really small number, it is solved.
I write this to help other people with the same problem, as well as to proposse a solution, which would be to check in WEBGui.showforces if any of the components is 0 and changing it to 0.000000001 or similar.