If there is no relative movement between the filter ring and the rear cell of the optic it is the grease absent or heliciod threads worn.
Even if you retain the heliciod entry points you will have to collimate the lens when you rebuild.
Many SLR lenses will work ok on different entry points, this would not be true for rangefinder lenses.
The last one I regreased a late series E 5cm collimated easily on different entry.
The build standard of the E lenses is good.