I had an similar issue in my 8.5 pro whereby I also get “extra” content added to audio when I bounce/export and import again eg. a kick drum will bounce and be longer then the orig.
I tracked it down to this - If I put any kind of Eq or filter or Compression on the Low Freqs of my Master Stereo out, it creates some kind of phase issues and makes low frequencies double up. So the kicks sound like 2 kicks badly mixed together.
Of course with a few sounds playing it totally Muddys up the mix.
As long as I do not use any FX on the master out Low Freqs I am ok.
Not very good if I want to actually master any of my tracks, or just mix them with compression or Hi pass. Thanks Cubase lol