Saving a film on MoviesJoys stores a reference to that film. It does not download the movie. The same distinction applies to series checkpoints: an episode reminder is not an offline episode file.
For a journey without a connection
Choose a viewing service that offers downloads for your account, device and selected title. Use its own download control and check the result before leaving. Some downloads expire or require occasional account verification, so read that app's current information.
Check the exact episode
A series download can fail to include the episode you expected. Confirm the season number, episode number and audio language. A quick check while still connected is more useful than discovering the wrong season on a train.
Keep the catalog list separately
Create a Watchlist backup if you also want a copy of your choices. That small text file serves a different purpose from a video download. It helps you rebuild the list in another browser, not watch the film offline.