unable to clearly hear others

Our church security team recently purchased several Motorola’s MR350TPR radios. We are using the 53727 Earbud w/Push to Talk Microphones. It’s very difficult understanding each other. We’ve instructed them to be careful not to place their finger over the three holes on the microphone part. We told them not to hold it too close and to speak normal. Still…hard to understand. One night I was in a quiet room calling to the main sanctuary right next to me and not one person understood me. Even when I tried it without my accent. lol

Any suggestions?

Do they all sound muffled or do they sound distorted?