The modified B737-700IGW that is now the AEW&C airplane for the RAAF has a couple of ventrals fitted under the aft fuselage, reason, additional directional stability during engine out flight.
The perception is that the vertical stabilizer is partially in the wake of the MESA antenna and is therefore not quite as effective.
In addition, they've moved both the elevator feel pitot tubes to the top of the leading edge of the vertical stabilizer because of turbulence left by the MESA antenna wake in their original position.
These are design features, not screw-ups!
Cheers, FD
