TMAG5253: TMAG5253 reading drift when no contact the metal

Tool/software:

hi Sir

I use the TMAG5253 to measure the paint thickness of car,  i will get the drift reading when no contact the car

but change to the HG106A,HG106A | 霍尔元件 | 霍尔传感器 | 产品 | 旭化成微电子 (AKM)

the reading is stable

please advise it,thanks