How to isolate two signals from each other if they use the same power source?
You need to add flyback diodes and base resistors to your circuit, and you need something more substantial than a 2N2222 as a driver.

Also, if the opamps driving the bases can't source enough current to drive the transistors into saturation, you might want to consider using N MOSFETS instead of
bipolars for the motor drivers.

Finally, if you're getting interaction between the two sides, it wouldn't hurt to stiffen up your 5V supply and make sure all your grounds are solid, or use a separate supply for the motors, still making sure all the grounds are adequately sized and solidly connected.