Well, good news: I believe I have fixed the problem! Seeing as I had the camera already partially disassembled to clean/investigate any superficial issues, I decided to break it down piece by piece and determine the origin of the grinding. The first component to come off was the lens mount and shutter unit; after removing this, I wound the camera ever so slightly and let it run at eight FPS just to take it easy on the thing. Lo and behold, no more screeching. Further, it seemed to be running at proper speeds; I dared not test it above forty-eight FPS, but eight, twelve, sixteen, twenty-four, thirty-two, and forty-eight FPS modes all functioned beautifully, which led me to believe it was the shutter making that God-awful racket. After a few minutes of my father and I (both lifelong tinkerers) examining the components of the shutter, we made quick work of disassembling it. While studying how it worked, we noticed that if the latch was held open, the shutter would freely spin (as it should when the shutter release button is depressed) and it would make faint screeching noises. Once the thing was apart, we lubricated the metal rod which the shutter was seated on, checked for detritus stuck in the mechanisms, put it back together, oiled it, and fired it all up.
Current condition? Quiet as a butterfly and completely operational. I must say that I am thoroughly excited for having almost completely disassembled, repaired, and reassembled my first 16mm camera. I couldn't be happier about it working, as I intend to take it (and my cleaned up Isolette I) to Spain when I visit a friend and film some of Europe while we travel. :)
