Epic
Hit the real Fortnite folder
Two Fortnite folders on disk is common. Swapping last year’s leftover looks like a broken app.
Settings → Installations
Epic shows the drive. Browse from there, not from memory.
Overlay
The overlay can keep a lock after you “quit”. Kill it from the tray.
Moving libraries
If you migrate Fortnite, retarget the swapper once.
Epic vs Xbox app?
Different folders. Point Galaxy Swapper at the Epic Fortnite you actually launch.