So constraint preview had a random crash because NaroCAD uses wrappers that obey to .Net virtual machine and this can break references in previews of textures, a functionality offered by OpenCascade using an indirect reference that .Net liked to destroy it. The solution was to stick references to used objects so .Net memory manager (garbage collector) to not delete it. The solution will create a transparent way to store this reference and a good part to it is that can be used in future to all other cases that may have similar crashes (yet this is the first case that was really necessary to not make a really custom development to make it work).
Another development based on work of Sami and bxtrx initially, enhanced, mapped and completed by myself is that points can be constrained. A full action will preview all points initially with blue, and you can constraint them by clicking them and they will transform with red color to know that they are constrained. After that the constraining will not be jumping.
See video here: (made with a virtual machine setup, so sadly it skip frames)