You really need to upgrade to 5.0.3 for Motion. Many improvements have been made.
If you don't see an update listed in the UPdates section of the App Store, then move the Motion app from the Applications folder into the Trash (but don't empty the trash until we're done).
Then launch the App Store, go to the Purchased tab, click the "Install" button to the right of where Motion 5 is listed. It will install the latest version, you will not be charged again, it's free to reinstall/update applications purchased from the App store.
After the install has been done, launch Motion. From the Motion menu go to About Motion and verify you have version 5.0.3 installed. When you do, empty the Trash.