Panning issue

Hello,
I got a problem with panning on audio files. I don't know when it happened or what happened, but after working fine for weeks suddenly some audio files at the beginning of my song have a strange behavior with panning. The signal only is on the left side. Means, when I adjust the signal to the right the signal is going low and at 100% there is no signal, when I adjust it to the left the sound gets louder and works fine. Before that issue I was able to adjust the sounds left or right and all was fine. It's only at the beginning of my song and applies to all audio files from part 1-5. Can anybody help?

Hey sanderxpander, you could be right, cause these audio files are placed on separate tracks. I'll give it a try and give you an answer again when I get home.