I’m guessing for the clipping you’re seeing, it’s because Wavelab 9 now decodes MP3 to 32 bit float, which is as it should be for analysis because that’s how Apple (and therefore Sonnox) do it for analysis. All prior Wavelab versions decoded to 16 bit fixed truncated.
You can either put a 24 bit dither in the master section to playback the converted MP3, which will probably eliminate the red lights you’re seeing, or you can save-as 24 or 16 bit truncated, since that’s how it was done in Wavelab before. Or render to 24 or 16 bit with dither. Any of those will probably reduce the clipping indication you’re seeing. The clipping will still be there in the MP3, which is why Apple accounts for it, but it’ll look more like your other players at fixed point.
Maybe there should be an option to decode to fixed point, because the new way brings in issues like this, that are possibly undesirable for longtime users, adding an extra step to get a 24 or 16 bit wav from an MP3.
But the 32 bit float convert should not be removed from a pro app imo, because it’s more correct and how it’s done for MFiT analysis. It was one of my feature requests. You can always go forward to 24 or 16 bit fixed point by render with dither or save-as (truncated), but you can’t go back to correct 32 bit float decode if the MP3 or AAC is initially decoded to fixed point.