Droolio

If you can’t find the original .torrent, one way to find it again is to use BiglyBT client’s Swarm Discoveries feature to search its DHT for the exact file size in bytes (of the main media file within). You may be able to find one or more torrents and simultaneous seed them with Swarm Merging too.

As well as the force recheck method others have mentioned, you can also tell BiglyBT to use existing files elsewhere when adding the torrent, which can copy the data onto there for you without risking overwriting the original files.

BiglyBT for manual dls on desktop, qBittorrent with the arrs

100% this. OP, whatever solution you come up with, strongly consider disentangling your backup ‘storage’ from the platform or software, so you’re not ‘locked in’.

IMO, you want to have something universal, that works with both local and ‘cloud’ (ideally off-site on a own/family/friend’s NAS; far less expensive in the long run). Trust me, as someone who came from CrashPlan and moved to Duplicacy 8 years ago, I no longer worry about how robust my backups are, as I can practice 3-2-1 on my own terms.