Why is the drone split into two drones during sitl simulation?

ArduCopter Copter 4.0
1

Hello, when I am using the sitl simulation experiment, when I try to modify the gpsDataNew.pos and gpsDataNew.hgt values in the NavEKF2_core::readGpsData() function, my drone will split into two. As shown below.
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2

hello,

red is the EKF position output, blue the RAW GPS position output

3

That is to say, the gpsDataNew.pos and gpDataNew.hgt values I modified are the RAW GPS position output?

4

Hello, where should I modify to unify EKF position output and RAW GPS output.