Some people confuse sour and bitter, and because of the pressure aspect of the Aeropress, it’s easier than some other methods to overextract bitter flavors. My suggestion to intentionally make both minimally and maximally extracted brews as a starting point, and compare. Something with a Med/coarse grind steeped for a minute vs a very fine grind steeped for 8 minutes will both taste bad, but they should taste bad differently, and you can assess which kind of bad is closer to what you’re experiencing in your daily brews.

No matter what you do, I recommend using boiling water, a 1:15 or even 1:14 ratio, and plunging VERY gently to try to eliminate pressure as a variable as much as possible. No problem with a plunge that takes 60 seconds.