Thanks for the video, but you were clear before so you can remove it.
Recently the way how the subscriptions are saved to the database has been changed.
First the database was updated after each portion of headers was downloaded, but to avoid overloaded the database with updates it's now done after all headers are downloaded. If you interrupt the download process by closing the app, the database is not updated and the already downloaded headers get lost.
This is a safer way to prevent headers being lost or that the subscription gets out of sync.
The side effect is that you need to download the headers once more, but you can ask yourself how many times you'll close the app while downloading the headers. The benefits outweigh the disadvantages, imo.
If the download takes too long you can also reduce the amount headers per download.