I have never entered the world of manuscripts (Biblical, rabbinic etc) for several reasons: lack of access, training, time--but not for lack of interest.
But I recently came across something interesting that I had to share.
Mishna Avos 5:32 is a good example of a 'famous' Mishna, one that quotes Ben Bag Bag saying that one should investigate Torah from every perspective, hafokh ba ve-hapekh bah.
The reason for doing so can be found in essentially three textual versions:
1) The most common one, found in most manuscripts and printed edition, the one usually cited is: de-kolah bah, "because everything is in it".
2) A second version found in manuscripts is de-kolah bah ve-kolakh bah, "because everything is in it, and all of you is in it."
3) A third, more rare version is de-kolah bakh ve-kolakh bah, "because all of it is in you, and all of you is in it."
As you can see, these are quite different. Why did Ben Bag Bag say "hafokh ba ve-hapekh bah"? I don't know exactly, but there are at least two possibilities besides that which we normally ascribe to him.