Meeko,
What you describe is certainly not right!
My very similar 36PD30 is nigh on perfect, and I consider myself very fussy, having spent 30 years monitoring a broadcast picture.
(I also use the excellent Ixos XHT601 with RGB from a Panny Digibox.)
If you have no other issues, perhaps a re-calibration is the answer.
(You might have a problem swapping, as PD50's seem to be getting rare.)
Good luck.