I have seen on multiple websites, mostly websites about seeing the Holy Land or otherwise pilgrimage-focused sites, that St. Jerome said:
If I could only see that manger in which the Lord lay! Now, as if to honour the Christ, we have removed the poor one and placed there a silver one; however, for me the one which was removed is more precious . . . .
The site typically prefaces it similar to the link above saying that St. Jerome, whose cave was nearby (since Jerome lived in Bethlehem at this time), did not approve of the 4th century replacement of the marble manger with the silver manger. Also quoted around the same point in the article is a "biblical scholar" who similarly disapproves of the "men's devotions" around the cave of the nativity.
I have yet to find a basis for this quote by Jerome. Do we have any record of this statement anywhere?
My search found a somewhat contradictory quote in letter 108, to Eustochium, dated AD 404:
I too, miserable sinner though I am, have been accounted worthy to kiss the manger in which the Lord cried as a babe, and to pray in the cave in which the travailing virgin gave birth to the infant Lord.
This quote suggests that he, at least some point in the past up to AD 404, was able to access the original manger. Perhaps the manger replacement came at a later point before his death in AD 420.