Why are some of my podcasts that I have moved into a playlist not showing on my iphone 6s

I have podcast subscriptions that download items everyday to my iTunes. I then select the ones that I want to listen to and move them into a playlist that I have created. I use the podcasts app on my phone 6s to listen to them but it only seems to have random items from the playlist actually showing. For example, at the moment I can see 17 in the playlist on iTunes but only 14 in the same playlist on the iPhone podcast app. This 14 includes some which I have previously deleted on iTunes.