Be careful dragging any sofa, the forces involved can almost snap a leg off if it hits resistance whilst being dragged.
I had an issue with Argos, got an independent report from a recognised sofa specialist, argos reviewed the report, swooped out the sofa, I also billed argos for the cost of report and my time at £10 per hour claimed that back also, kept all evidence for use in small claims court if it came to that
These look like standard DFS sofa legs they normally screw in and are fixed in place with a screw. It looks like the mount the legs screw on to is broken. If you have kids who jump on the sofa it might be worth asking for a different design ( just a comment your kids might not jump on it)
How did you make payment?
I very much doubt it'd be 'secretive', just DFS' covid policy