Yes - already been there done that! everything up to date on all devices. But exploration does show that, although the episodes play fine on my MacBook the affected ones look 'odd' in that although listed normally in the TV app they do not show a thumbnail, nor do they have a cloud download icon, as other episodes do. But adjacent episodes that work normally show exactly the same purchase dates and times (24/06/2016, 16:30) as one might expect - so why can I not just stream them anyway regardless of file locations?
To repeat - everything looks and works fine on my iPhone (14Pro OS 16.6). I note that USB syncing with this does NOT restore episodes to the MacBook.