Works for downloaded files, not ripped files

It's probably interlaced. You need to process it before SVP can work with it.

That, my friend, is a long rabbit hole to go down.

In a nutshell, first you have to identify what kind of interlacing it has, then apply the appropriate deinterlacing. Re-encoding is one option, but you can also apply it in real time with an AviSynth/VapourSynth script, or even the ffdshow raw video filter SVP comes with.

I'd offer to analyze a test clip myself, but I'm on a phone atm

MakeMKV's job is to rip video files from DVDs without changing them at all, and that's exactly what it does. The DVD is interlaced, you'd get the same results playing the file straight off the disc.

A few video players have deinterlacing options, but personally I would just find the SVP script (normally in the ffdshow raw video filter during playback) and insert a deinterlacing line before it. TIVTC if it's telecined, or Faster/Very Fast QTGMC if it isn't.

Also, I should mention that this is a minor flaw with SVP. MadVR is very good at deinterlacing, but unfortunately it runs after SVP. As of now, integrating them to let MadVR do the deinterlacing is impossible.

I'm looking at the FDDshow video decoder options and I'm rather lost on what to do next to "add a deinterlacing line" I see where it says

global svppath="C:\Users\Robert\AppData\Roaming\SVP4\"
try {
   import(svppath+"scripts\7074c.avs")

But I don't know what to insert.

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Edit: I did find a solution in the moment. I can run the file through Handbrake with the Decomb filter, and it works!