I had a previous thread on my issue but never managed to solve my problem.
V3.8 has cured my particular problem.
Problem: I normally use a single stereo file with click on the left and music on the right. I liked the fact that tempo or pitch can be changed in ST3 easily, however, every time I had to change something, I would get distortion on the click track accompanied by some bleed through of the music onto the click channel. Not a problem affecting front of house feed but annoying for me in my ears. I had to address this by making changes outside of ST3 and replacing the ST3 file.
I could also reproduce the issue if I applied a stereo plug-in on the master channel to the file when preparing in Logic. e.g. applying the pitch alteration or compressor on the master stereo output - so I assume that a stereo plug-in was somehow causing the distortion/bleed between left/right channels only when playing the file back in ST3 as the file sounded fine through headphones through Logic. Only way to ensure this would not happen was to apply a mono plug-in on the music channel itself and not on the stereo master. I had the same issue when preparing the file in Audacity, so I don't think it was Logic at fault.
Cure: V3.8 now allows changing tempo and pitch on multi track songs, so I tried one of my tracks by separating the click and music onto different files (in Logic) and using the multi track facility. Now, when I route both files to the stereo output and pan each left and right as appropriate, I am able to adjust tempo and pitch without the adverse affect I was getting before. I couldn’t try this method before as V3.7 didn't allow pitch and tempo changes on multi track songs. Using a single stereo file however still resets in the same issue.
Only wish I knew why it was happening in the first place as it doesn't seem to be a common problem and is likely something I am doing wrong in my process.