Update:
Deleted com.apple.quicktime.plugin.preferences.plist and QuickTime preferences, both located in /users/username/library/preferences, then restarted computer.
Following that, deleted Final Cut preferences, OBJ cache and Prof cache files located in /users/username/library/preferences/FCP user data/
Result: scaling down a clip using “Scale” on the Motion tab now works fine, without the loss of quality that was occurring previously. However, use of the “Replicate” Filter still results in the same loss of quality as before.
Any suggestions would be appreciated. Thanks.