I did more testing and I don't think this is a bug. The F-16 A/L and F/R tank capacities are different. A/L tank will fill first and apparently doesn't crossfeed to F/R. When the A/L main tank is full ~2330lbs the left side of the jet's fuel system stops filling the A/L main tank while the right side fuel system keeps filling the F/R main tank to ~2770lbs (440lbs more) causing the right external tank and the right wing tank to keep feeding. This causes the fuel imbalance.
