Basically, there are only two ways that you can get this error. The main cause of this error is the corrupted torrent file and the only ways that the torrent file can get corrupted is as follows: Your ISP corrupts the file as many ISP now days are corrupting torrent file because of Government restrictions.
HELPFUL LINK: https://www.geekdashboard.com/unable-to-load-torrent-is-not-valid-bencoding/
Hope this helps !!! ... 😊