The buttons for the legs & hitch aren't the only things missing.
Where those 2 holes are either side of the collector - there should be 2 more buttons, as well as 2 conveyor sorters & 2 ejectors.

What you're looking at here is a really early version. It wasn't even on the workshop when it looked like this!

I've only updated the BP once since it's been published but only the tractor was altered. I swapped the connector on top for a collector and changed the conveyors around a bit.

Wait... does the tractor have a connector on the top or a collector? I'm gonna bet that somehow you have a whole different version to what's published. How is that even possible?!

Just to rule it out as a steam client issue, have you tried unsubbing, deleting the files off your drive, then re-subbing?