Audio issues on MK2 450h

[abtx]

I started experiencing weird audio issues, like the volume goes up and down, crackles, and, if I'm using radio, sometimes it will seek next radio station on its own. CD sometimes does work and the sound is perfect.

Here's a sample video of how it sounds on radio (and aux): 

Lexus priced me at 2k for replacing the whole unit, and eBay has lots of second hand ones for ~10% of the cost, but they all look slightly different to what I have. 

I could either fix the whole thing but this can prove to be difficult. Is it possible that the amp is responsible for the volume/crackling, in which case I can just replace that for now? Anyone had similar issues? 

[Herbie]

When you say the CD "sometimes" works, how often is sometimes? And on the occasions where it doesn't work, is it the same problem?

If the symptoms are the same then it could be the amp as that's common to both forms of input.

[abtx]

Sometimes is rarely, really, and then it seems that I cannot skip between tracks. When it works, the aux and radio have the same issue. So symptoms are different between sources, ie. CD sounds always great when it works and aux/radio always sounds bad. I ordered new head unit, but w/o a cd charger. Will try replacing and see if that solves the aux/radio issues.