One sided signal from headphone jack (CI2+)

Hi everyone.
I’m using the CI2+. Since I don’t have any studio monitors, I’m running my normal stereo through a 6.3mm (1/4’’) cable into the CI2+ ‘s headphone jack.
The problem: the signal only comes out on the left side of the speaker. I’ve tried headphones, too (with an 1/8’’ to 1/4’’ converter) but I get the same results.

Can anybody help?

I have the same issue here. Anybody with an idea?