I have no time to write down the details how I discovered the problem, but here are the results of my investigations.
I created a 1 bar file of audio click
Laid it on four different tracks with four different track delay settings: Track1: 0ms, Track2: -6ms, Track3: -12ms, Track4: -24ms
Exported the main out buss for all four files (by soloing one at a time).
The audio data in the resulting files showed the following delays compared to the original file (with 0 delay):
Track1: 0ms, Track2: -12ms, Track3: -24ms, Track4: -48ms
So, it seems that negative track delay values get doubled when exporting audio, placing the audio to a wrong position.
Conclusion: Never use the track delay function to compensate the delay of multi mic setups, because the exported audio will get screwed up. Actually, never use the track delay function at all if you plan to export the audio (I guess always).
I’m sure this error will be present in C6, too.
I haven’t tested it with positive values.