There seems to have been a bit of a mix-up in one of the numbers:
Step 15. The instructions say to slot parts 54 and 55 together but the actual pieces are labelled 55 and 56.
I’m terribly sorry about that.

This is the instruction video for the latest version of the Magnificent Marble Machine. It looks much the same but with a few small refinements to make it easier to assemble. The way to tell if this is the video for your Machine is by looking at the code above the barcode on the back of the box. If it has an ‘a’ on the end then this is the one for you.