Hi, I don't have one of these so can't help directly, but I do have some experience of shapers. Looking at the pictures on lathes.co, it seems to me that there must be some way of getting the captive nut off the table. Sometimes the captive nut has a round part that just pushes into a hole in the table. Of course such a hole may or may not go right through to the top of the table, you would have to take a look. If it does not, then you would have to get the nut to come out from underneath, which seems a bit tricky, as would be the assembly in the first place.
Maybe if you have a dentists mirror you could have a peer underneath.
John