Hello,
Thank you for the detailed description of your workflow. The focal length estimation is known to be somewhat fragile in UE 5.3 (and before). A big focus for us in 5.4 and 5.5 was increased accuracy of focal length and nodal point calibration. I’m not seeing anything obviously wrong or faulty in the setup you described, but I’ll discuss with the team to see if we have any ideas for workarounds.
Have you had an opportunity to try your calibration setup in UE 5.5? I would be very curious to know if you are able to get any more accurate results.