How are you doing? I see you haven't had a chance to reply yet. I'm sure it's a minor thing to sort out, and I know Gütermann thread is no problem on the older machines be it, 1920s, 1950s or 1970s. I think the standard was set way before the 1970s, more like 1950s. The problem with thread is mostly uneven spinning, bumps in the fibers, and a couple of times I've had spools of unreasonably weak thread, snapping in two for no reason. Polyester thread tends to be very smooth, and Gütermann is the one with least fuzz and lowest lint production in the feed dog - bobbin area. Lower priced thread tend to have more fuzz along the thread. If the machine is new to you, or it's a long time since you have used it, it's probably all about finding your way about the settings.
Your avatar pick is fine, is it from your garden?