I had exactly the same issue and that was the reason. To remove it take a needle or a pin it's not very hard push the needle to the edges and eventually will come out. Found this video though it's not mine!

https://youtu.be/kDcKnM9fK4w

I had the same issue with mine. I can barely hear the left one. Filed a warranty claim and sent them back

My left bud is much, much quieter than the right. I'm 99% sure the issue is wax in between the grille and the filter, but I've been unable to remove the grille to clean it. Has anyone been able to remove the grille?

How do you remove the metal grille on the Buds2 Pro?