different reading in different probs

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Hi
Iam using vastXT probe head which doesn't rotate, When using probe number 1(vector direction z plus)I got 0.21 form error, while checking same plane (I fix the job in different orientation)with same number of points with probe number 5 (vector directory X minus direction) I got form error 0.24. I calibrated the probe all of them have 0.0003mm error maximum.This is problem in machine?? Machine calibration pending for 4 months.