Cubase 5, internal compressor error when exporting

Hello there!
I’m a user of Cubase 5 and I have just tripped over an issue I can’t find a solution for.
These days I’m mixing a project and I have made extensive use of Cubase’s own compressor. Today I exported a drum bus and imported the resulting track into the project so I can disable some plugins and save some resources. I noticed it didn’t sound quite right, so I inverted the phase in that track and played the drums bus at the same time. The sum didn’t cancel at all. I had a loud sounding V shaped kind of resultant spectrum. I have spent several hours looking for the cause and I think I have found it: One instance of the compressor was used in the kick track and another one in the overheads track. If I disable those plugins the exported drum bus is identical to the one I hear when I play the song. Is this error documented? Is there any solution to it?


More tests.

I tried setting the output of the bus drum to a new audio track and recording the output as the song played. The resulting recording is quite different from the audio I hear, a relevant amount of the high frequencies are missing, along with transients and part of the stereo image. When played back along with the drum bus I can clearly hear it yields an important residue.

I have reopened the project in Cubase 7 Elements and made a new export from there. The error is smaller but still evident, the 2 tracks don’t cancel each other out either.