Pentax MX shutterproblem

One of my old MX:s is giving up? Shutter works great at long exposures, 1/30 and longer. But from 1/60 and shorter only about 1 quarter of the image is slightly exposed. Problem started random now all the time.
Is this serviceably? Or is the shutter just defect and about dying. Another one bites the dust ala Queen! Camera works otherwise perfect. Low serialnr. late 1970. My other MX is later from about 1980 and still works perfect.