Hi.
Wikipedia says:
"Jonson is buried at Poets' Corner in Westminster Abbey, with the inscription "O Rare Ben Johnson" (sic) set in the slab over his grave. It has been suggested that this could be read "Orare Ben Jonson" (pray for Ben Jonson), which would indicate a deathbed return to Catholicism, but the carving shows a distinct space between "O" and "rare"."
Not sure if this explains all, but it's an idea anyway.
JimC