Lewm and Slaw are correct. Using the placement of a vocalist in the mix is not reliable.
And if your problem is not electronic you could be obsessing over something that could have you chasing your tail for some time, instead of enjoying your records.
Here’s something that happened to me.
After upgrading my turntable table in 2020 I pulled out a test record I had picked up at a used record fair for $1. My main purpose was to check the anti-skating. But a couple of tracks also helped me to evaluate channel balance, which up to that point I thought was just fine. Turns out, it wasn’t, It was skewed noticeably to one side.
Even though my speakers are are equidistant from the side walls and the wall behind them my room layout is asymmetrical. I have CD racks on one side and records on the other and the location of doors, windows, electric outlets together with media storage dictated placement of everything that goes against a wall. I am convinced that this is what caused the sound to tilt a bit to one side.
The test record and the balance control on my preamp helped me to solve the problem. And when I did, it was like… aaaaahh.
Your preamp’s balance control will set you free.
As God and the manufacturer intended.
Peace and long life.