So this could be a few things. First make sure you are using the correct ST for the game. Some users use a single ST for all CoD's which I don't recommend due to the small differences in deadzone and micro movement mainly.
Some users have reported issues like this at certain dpi settings. You mentioned trying all dpi levels.
Next you could consider the surface you are using. Laser mice track better on hard surfaces, optical on soft. Also check the sensor for debris. I know you mentioned two mice so probably not this.
The G402 has a surface tuning wizard inside LGS. There are presets and a calibration tool. Users have reported having tracking issues until they have played with this setting so it's worth looking into.
If you are using the correct ST and this doesn't happen with a lower sensitivity then you may just be experiencing unstable movement because of the very high sensitivity and dpi setup that you use. I'm curious about this because while MW2 is an early tech ST, MW3 is not.
Can you describe the type of movement you are seeing? Do a sweep with your mouse but start slow and build up speed. At what point does it occur? Is it skipping or zig zagging? Does it happen only when targeting enemies or does it happen when there are no enemies around? Hip, ads, both?
