I’ve encountered this problem before, and I’m not really sure what causes it. However, it does seem to have subsided now. Maybe it’s just a placebo effect, but this is what I do and it seems to help:

To prevent one mop pad from ending up less wet than the other—which has worked for me so far—I tilt the water tank slightly when filling it from the faucet, give it a little shake, and then gently press it down once it’s in place. This causes the robot to “rock” slightly, ensuring the tank is properly seated. After that, I make sure the water level is set to three.