Reply To: Problems rotating the lid planks (about 7:21 in the Sharing objects… vid)

 I guess I must have changed them somehow along the process

Indeed; your top is no longer cylindrical, but squashed on the Z-axis:

I’ve added a Cylinder, so you can see the difference in height. You can also look at the Dimensions in the N-panel; the Z should be half the Y (Dimension), so: about 1.25 and not 1.05.