Why can’t I re-download clustertruck (a game I previously installed) for free now I have to...

Clustertruck was on Game Pass. It no longer is, hence why you now have to pay for it.

Ok so I cleared the cache... uninstalled... re-installed... NADA!! so I then moved the file to a formatted USB drive and tried playing it from that.... works fine... So I'm thinking my Hard Drive either needs re-formatting or replacing?

Strange because it's only slow on newer downloads... all previously installed games run fine?? and I have at least 49GB left free??...

It'd be a pain in the **** to have to reinstall 40 games and their add ons just to reformat :/

I'll play it from the stick for now I guess?

^ I still don't think it works that way. You are "Gold" now, so you get the game free now. Once you've downloaded it, the game is in your Download history. If you decide not to re-up your Gold next month, the games will still be available to you to download
later because you have "purchased" it previously.

Yep I can't download Full Glasses, Full Colors, The free BGM #1, and the Update 1.30, Which I have had downloaded before, now I can't re-download them. Goes 1%, 0%, 1%, 0%, "Can't download -so and so content-" I had all this purchased and installed. I had
trouble with the full color pack, and I tried to delete all DLC in an attempt to make it work, but now I can't download the stuff I previously mentioned.

You can always redowload your games by going to settings => profile => download history, i think this solves your problem