I bought a new SM3 and it's in pretty nice condition. It's a 1956 machine, but it's very clean and types well. However, the auto-reverse function on the ribbon doesn't work. The eyelet will be pulled tight against the ribbon guide, but the guide won't shift like it's supposed to, so I'm only made aware of it when I notice my text is faint and spotty. When I use my fingers to manually help things along, it works fine, so I think it's just a lubrication issue. Is there any specific place that I should look to clean or apply some oil? I know these are common and beloved machines, so I thought I'd inquire here to see if it's a known issue before I start trying to take anything apart or throw oil at every likely-looking linkage. 

Thanks!