904 transmission

It definitely sounds like the problem is with the linkage which should come as very good news, IMO.

I don't see how the console being loose would be to blame as the shifter is secured through the mounting legs. First, I would remove that set screw (put it in a baggie and bring it with you to the hardware store) and get a new matching one along with some Loctite.

Then I would remove the console and make sure the shifter assembly is not loose.

I don't have a console car so I'm not certain but you may need to pull the carpet back in order to see everything.

If everything checks out, put the car safely up on some ramps and follow the shifter linkage and see if there's excessive play in any of the links. It's a pretty simple design so I imagine that it would be easy to spot.

If that all checks out, I would remove the linkage all together and see if you're able to move the transmission through the P/R/N/D/2/1 by hand. It should click from one position to the next without too much force.