First, if you have not already, go to Tools, Camera Calibration, select all the images and enter 10000 for both fx and fy - that is 120 mm / 0.012 mm
Enter 3840 in cx and 6912 in cy - those values are 7680 / 2 and 13824 / 2
Select Fixed for Calibration mode - make sure you hit Apply
Now go to the Ground Control panel and import the file you have with N, X, Y, Z, O, P, K
Make sure your image names include the file extension or the name won't match.
Under settings in the Ground Control panel set your camera accuracy to 0 if you like, at least for starters.
I would go ahead and do an alignment and use High and preselection of Ground Control.
After alignment, use Gradual Selection and delete selected points, then optimize - repeat until bundle_adjust is around or less than 0.3 or so.
Perhaps loosen the Camera accuracy and see what errors you have - it is a good check on your previous solution. The results will never agree exactly with any other AT result, but the errors should be about the same- again a good check.
If you have a ground control file, import it and have PhotoScan create markers for you. Go visit where the markers are projected to and perhaps even pin them for another check.
If you do mark the control in PhotoScan, uncheck the cameras as control and use only the ground control. Check the errors against what you had before. By then, you will have a pretty good feel for what is going on with PhotoScan
Tom