An airplane I'm working on has a tendency to slowly roll to the port. It has two turbofans on the wings. It's a completely symmetrical plane, but when I checked, the CoM, CoT, and CoL are all a few inches to the port, despite identical engine performance, weight, and wing area on either side. I play on Android. Is there a logical explanation, or is it a bug? If it's something I did wrong, how can it be fixed, and if it's a bug, how can I counteract the effects? I would greatly appreciate any help.