Lag during roof editing in X6

[Glenn Woodward]

Try turning off Auto Rebuild Walls/Floors/Ceilings in 3D View Defaults - I think that's what the dbx is telling you.
You will then have to rebuild manually though.
You could also make sure you don't have any of the auto framing options toggled on.

I think the only reason you see the message on large plans is that it takes so long to rebuild.
The message probably still pops up with smaller plans, but it's so fast, you don't notice it.