Llowllife

I have an old Canon 55mm FL lens that was modified to fit an EF mount. On my 5D mark ii, it looks magical at f 1.2. But my C100 mark ii can't decide if it's AF or MF, and if it's f 1.2 or 8, so it just flickers between the two settings. This makes the image flicker too. I'm sure this can't be good for the camera, but I can't figure out how to change the camera settings to accept the lens. Any advice, suggestions or insights?