Are you using a Pocket door from the Door tool? When using the "Flip Inside/Outside" feature nothing happens on a Pocket door, as it's in the middle of the wall. The best I can see is to use plus or minus values for "Frame Inset". This will move the pocket door to one edge of a wall or the other.
Designer, Deluxe, (Basic, Expert, Professional), Platinum
Windows 10 Pro (1909), 64-bit