I found many coasters didn't work for me, but I did find some heavy duty rubber ones that did the trick.

I wonder if you can flip the thing over and attach a board to the underside to bolt it together? Might sound drastic, but I bet it would work.

are you sure the rods are locked in place?

other than that, the board on the bottom is a good idea. if you have something solid to screw it in to.

the rubber furniture feet could work well for you. you could also use the spray on version of plasti-dip, though i'm not sure how well that would hold up, and wouldn't want you to scratch those pretty floors!

Rug pulled out will look fantastic if you can keep your sectional together somehow. You have a great space :)

If the sectional did not come with a locking devices, go on the internet and purchase them. They are cheap, and easy to install. Best place to find them are upholstery supply sites. You might also go back to the store you bought it at and tell them the pieces are separating.

Have you checked out Sofa Snap - by Homeplace Group - they keep sectionals from separating. They have a bunch of models if you need a different kind - just make sure when you purchase them on Amazon or Ebay, you get them from Homeplace Group. I've noticed other sellers that are using the name, but not selling the actual Sofa Snap product.