I have had an M3 serviced early this year but have only just finished the film and developed it. About 9 out of 36 exposures suffered a similar light streak although one had it in the middle. The rest were okay. Most photos were taken at 250th & 125th. It looks like the closing curtain is not going into the opening curtain channel correctly. Is this a simple fix like cleaning the channel and applying the barest of lubricant to the channel? Or tweaking the tension a bit on the closing curtain? Otherwise it's a long drive to the service guy on the other side of town.