Had the Pimax 4K since Dec. 2016, Pimax would release updates that seemed to make the 4K's quality suffer more and more including ghosting.
Ended up settling on Piplay 1.1.92 after various attempts to see what the new updates brought.
Unfortunately, 6 months or so later after too many disassembles/reassembles, the Pimax 4K simply had enough and it gave up on me.
Ended up buying the Rift CV1 within 2 weeks & re-bought the 4K within 6 months or so.
No positional tracking, ghosting, dull panel & no controllers and still, the 4K was re-bought because the Rift CV1 simply could not compare but distant objects were more easy to see.
OLED, Touch controllers & positional tracking, nice but the SDE on the Rift CV1 really annoyed and still annoys me.
Experimented with various input/positional tracking options...
Fast forward to now and what do you know, the Pimax 4K is still going strong with added VRCovers/Vive wands/basestations & trackers.
It took a while to become satisfactory in other areas from 3rd parties...