I scanned my car with photogrammetry and moved the pointcloud from colmap to blender, to reconstruct the faces by hand. All worked fine in version 2.79. I had the pointcloud visible as orientation in one object and in another object (reconstruction-face-object) I drawed vertices, that snapped to the vertices of the pointcloud (to get that position). Then I updated Blender to version 2.92.0 just to use a photogrammetry plugin, which gives me the advantage to add an extra OpenGL Point Cloud with colored points (only for extra visible orientation), next to the normal pointcloud and my reconstruction-face-object.
My Problem in version 2.92 is: If I try to make a new vertex in my reconstruction-face-object and move it to one of my orientation pointcloud verteces from the other object, it first snaps there, which is fine but then jumps to the nearest vertex of my reconstruction-face-object if I confirm the transformation and if the distance is too low. With higher distances to any vert of my reconstruction-face-object, there is no problem with that workflow. I tried to figure out how to decrease the sanpping distance, but only found grid snapping stuff. Do you have any idea how to solve this?