iTunes cannot transfer movies bought from the Store onto the iPad.

I have an iPad Mini and iTunes cannot transfer movies bought from the Store onto the iPad.

'Manually manage videos' is ticked but then after each sync attempt it goes back to being unticked.

'Sync only checked songs and videos' is also ticked and remains so.

When I choose the movies to put on the iPad, it gives me an indication of how much space I have (enough), lets me sync and then goes back to zero.