I ran into a problem that I wanted to share because it took me a long hours to discover the problem.
Seems, that P4RTK has different camera models and even latest Pix4Dmapper (4.5.6) does not have all of them in database.
When I imported pictures, Pix4D automatically recognized cameral model P4RTK, but after initial processing calibrated camera computed positons some of them were wery wrong locations and after final processing the point cloud was very stretched / very wrong. I did all other tricks what advice I found - Keypoints half image size, matching geometrically verified and calibration all prior etc. Nothing helped. Last thing I looked camera model parameters, imported from EXIF and wow - this is where the dog is buried.
From Pix4Dmapper 4.5.6 database
And from EXIF
Now the results are perfect !