"Package generation failed" converting RS1 .dat to .psarc - Song Creator Toolkit

Hey guys. I'm not particularly good at any of this and I'm at my wit's end.

After much trial and error I finally got the SCT to convert my old .dat file. It creates the folder, fills it with all kinds of nonsense, and then seems to do a bunch of stuff when I hit 'generate'.

After that it asks me to save the file. So I do. And then it kicks me an error, interestingly it's the same error here:

https://github.com/rscustom/rocksmith-custom-song-toolkit/issues/357

Now what's interesting is the comment: "RS1 cdlc have been converted mostly and already has it's version over CF". Okay, this doesn't seem to be the case? Or is this referring to something else - because I just want my Rush songs back (I only just got back into this and found I missed the boat on the Rush songs by six months, assuming I wanted to buy them again (which at this point I would have because this is frustrating as hell)), but the CF library has all the songs I had locked out because of 'piracy' policy (more like abandonware at this point but whatever).

Okay, so.

What do I need to do differently here? What is this error? How can I get my songs back?