Hi, my name is Alex, I'm from SyncMate team. Ed, we cannot say what exactly caused the duplicates (we need more details to investigate this issue and need your assistance). But according to information you provided in your post, we may assume that you have Google sync option enabled on your device. So, when you are syncing data in your Mac and Android, your Google account is automatically synced with your Android and that's why you are getting duplicte entries on your mobile (take a closer look at your appointments, even if the same entry differs in one letter or symbol in Google calendar and iCal, SyncMate indicates it as a different appointment).
Our advice is to disable automatical sync of your Android with your Google account (it can be disabled in your device's settings) and sync data again. If this won't help, please, contact our Support team (support @ eltima.com) for further investigation.
If you need to sync data in your Mac with Google also, you can sync it with SyncMate - just add new connection => Google account.
