Launchbox doesn't pick up games sharing the same name and the same platform when searching for metadata - if there are two games with the same name, released on the same platform, it will only find one. This is a problem with games like Attack for the Arcade (one was released by Taito in 1976, the other by Exidy in 1977, they're completely different games), or Heavyweight Champ (1977 release for Arcades by Sega and its identically named sequel from 1987).
The games are working ok in the database - they have unique ids and display as separate titles when searching on the site, it's just the Launchbox app that returns only one of them when searching for metadata. This is a problem, as you can't bind the other game in your collection to the corresponding entry in the database.
One idea to circumvent this would be to add the developer name in brackets in the title, e,g, Attack (Taito) and Attack (Exidy), but then it still wouldn't work in the case of Heavyweight Champ (both games release by Sega). This should be fixed I believe - there may not be too many games that are affected by this bug, but they still exist.