Podcasts deleting

For the past couple of weeks my iphone 14 plus on ios 16.4.1 has been deleting the majority of my podcasts. I currently have over 80gb of free space so memory shouldn't be an issue.

I keep my main catalogue on a hard drive and download the podcasts to that and then transfer them to my phone via itunes. I usually have about 400 podcasts on my phone so having to re transfer them is an annoyance.

So the usual pattern is I update the podcasts and everything is fine. Then I use my phone and it is fine, all still there but after a day or so, not sure on exact timing as I don't alway use my phone daily to listen to them, when the podcast I am listening to ends nothing starts. I look at the screen and it says that mobile data useage is turned off and when I look all the transferred podcasts have gone. Those that I have downloaded directly to my phone are still there, but the 400 transferred have gone.

I have tried different settings but it still seems to happen.