Many downloaded (complete) files have no trackers

[PinBalldr]

I currently have about 225 completed torrents in qBittorrent5.01 (had run 5.03 with same issue) and found at least 20 torrents not uploading. I tried attaching trackers from other torrents and this helped for current session.
My questions are;

1. what happened to the trackers from the download? I guess (assume) they had some when I downloaded the files.
2. Will these trackers stay attached the next time I have to (or windows update) reboot the computer?
3. How can I prevent loosing trackers that are / were attached in the future?
   I tried searching this help section and did not find anything like this.
   Windows 11 pro,
   Avast VPN - since I download and upload other files, I don't see this as problem with loosing trackers...
   Thank you in advance for your help

[thalieht]

I guess (assume) they had some when I downloaded the files.

You shouldn't.

Will these trackers stay attached the next time I have to (or windows update) reboot the computer?

Yes, trackers can only be removed manually.

[PinBalldr]

" I guess (assume) they had some when I downloaded the files.

You shouldn't."

Then I don't understand how the download works without them. Do you have a link where I can learn more? TY

[thalieht]

Then I don't understand how the download works without them. Do you have a link where I can learn more? TY

DHT, PeX, LPD