That should absolutely not be the case! If one earphone is quieter, the localisation of vocals, for example, should slip away from the centre towards the louder side!
If the same problem occurs with the second cable, then something is wrong with the headphones!

I don't have this problem. I have been using the headphones for a long time. As these headphones have a replaceable cable, I suspect that the plug connection does not have a clean contact. Try cleaning the contacts or use a different cable (2 cables should have been supplied). I think this should solve your problem. Greetings and good luck Peter

Not until now. I've had it since August 2021.