My guitars are louder on the left channel. What to do?

I'm an extremely newbie user of REAPER, and I know nothing about mixing. While recording some guitars, I noticed that the guitars panned to the left are louder than the ones panned to the right. I thought it was an issue with the tracks, but it isn't, as, if I change the panning on the same track it still sounds louder on the left. If I pan it in the center, the VU Meter shows that both sides are equally as loud, but I can hear a net difference in loudness. I'm using a guitar amp sim (amped roots), and if I export the project, the issue persists with every single device I play it on (car, phone, computer, headphones...). What to do?