I have the same overjet as you, on my left side I have 8 mm overjet and on my right side I have 4 mm. This was not something I had before braces but my teeth were so tight together then and my arch was like a Ω and when my ortho made it to a U I got this strange overjet.
The reason I got this is because I had 7 teeth on my left side and 6 teeth on the other side (the premolar on the right was extracted when I was young).
I extracted a premolar on the left side and we are moving my teeth back. In my case I can´t see any other options to fix this without extraction but it might be different in your case. Why not ask another ortho´s opinion? I would do that if it´s always on you mind.
Can take a picture later to show you if you want. It´s so funny to have this overjet because it´s so huge on one side but the other side is “ok”

looks so strange! It´s "funny" now because I still have braces and know this will be fixed. It had not been funny if my treatment was finished and I still had it though...
Good luck! And yes, please keep us posted
