First, not using supplied mux lists was a good Idea to shuffle away Problems with not finding all Channel, because as you found out they can be a little oudated, and if you dont use "New muxes + changed muxes" under Configuration > DVB Inputs > Networks > Your Network > Edit > Network Discovery, it will by default only Scan for "New muxes" so outdated Channels wont be found when Scanning. So to really find all Channels it is in my Opinion the better way to scan the whole Network manually, but thats just my Opinion,
As for your failed Login, is it really right that your user for TVH Frontend is "hts"? I ask because normaly the user hts is just the Linux System User for TVH itself. Anyway, i just ask to be sure your user for TVH Frontend is really hts because the "403 Forbidden" clearly states that either username or passwort you used was wrong.
And at last, for the Problem that the File you wanted to Download gets moved to Failed Recordings, have a look into the Logfiles of TVH and search for what really happens and why it happens. Also have a look what it is saying when you try to login when it fails with "403 Forbidden".
Anything further here would just be guesswork and wouldn't help either you or us. 😉