I was playing at church for a while as a beginner. The first three times I played I really struggled with keeping in time. The forth time I asked a friend who has been playing for years to come play. He informed me that my issue wasn't me, it was the drummer that couldn't keep in time.
The next week I wasn't playing, so I really paid attention to the drummer. He was singing and switching to drumming the melody and then back to the rhythm. Once my friend pointed it out it became pretty obvious why I couldn't stay in time.