Atem constellation Pan changes all the time

We have an Atem Constellation 2K and use it for livestream.

We use a seperate Zoom L12 mixer and Sennheiser beltpacks for audio.

Everytime the pan (balance) from the TRS changes, so every time I turn on the set I have to change the pan to more to the left, and sometimes more to the right.

We tried different cables but it didn't work. It also is not the pan on the mixer which is in the center.
I tried googling but couldn't find the issue.

Does anybody have an idea?

I have a couple of ideas that you could look for:

First check the L12 pan settings. While you probably already know how to do that, I will list here anyway:
For each channel that you are pulling an input from, hit the "SEL" key for that channel (it's got the color blue around it). Then look to the "PAN" pot on the L12 (also got color blue around it). Make sure that it is only centered. Look closely because on the L12 (and the L20) you can be slightly off center and the next set of lights just light up very faintly.

Next, you mention that you have checked cables. Are you using an XLR from the L12 to 1/4" into the ATEM 2 M/E Constellation. Is it a single cable, or is their an adapter cable or adapter barrel in between? If yes, try switching those as well....I have gotten different volume levels with different cables and adapters. An easy way to test that would be to just leave everything the way you normally do....and if you notice that the Left channel is louder (as an example), just switch your left and right input. IF you know have louder audio on the Right channel then you can rule out anything on the ATEM and start looking at cables and L12 settings.

Thanks for the fast and extensive reply!

I won’t be in the office tomorrow but will check on Thursday and will keep you posted!

I have a couple of ideas that you could look for:

First check the L12 pan settings. While you probably already know how to do that, I will list here anyway:
For each channel that you are pulling an input from, hit the "SEL" key for that channel (it's got the color blue around it). Then look to the "PAN" pot on the L12 (also got color blue around it). Make sure that it is only centered. Look closely because on the L12 (and the L20) you can be slightly off center and the next set of lights just light up very faintly.

Next, you mention that you have checked cables. Are you using an XLR from the L12 to 1/4" into the ATEM 2 M/E Constellation. Is it a single cable, or is their an adapter cable or adapter barrel in between? If yes, try switching those as well....I have gotten different volume levels with different cables and adapters. An easy way to test that would be to just leave everything the way you normally do....and if you notice that the Left channel is louder (as an example), just switch your left and right input. IF you know have louder audio on the Right channel then you can rule out anything on the ATEM and start looking at cables and L12 settings.

So I checked all the pan settings on the L12. They are correct.

I also changed the cables from the Zoom from left to right..., and the pan is still the same on the Atem.
So this would mean it has nothing to do with the L12 or the Cables if I am correct?

It should be something in the ATEM Then, but how? And what?

How do you monitor the audio? In other words, where are your headphones plugged in? The Atem 2 constellation doesn’t have any headphone jack so you must be using some other piece of equipment to monitor.