I sent an old sefer to be fixed in Israel. I received it back this week and one omud has a matlis (patch) with about 12 letters written on the patch. the last letters written before the matlis, a daled, extends a little onto the matlis. When I asked the sofer about this he said that he originally wrote the daled so that ended before the matlis and was mukef gvil. However afterwards, he went back and made it a bit longer so that it would be closer to the letter after it, so he extended it a little on to the matlis. but since b'shas ksivah it was mukef gvil, he argued that what he did afterwards was OK.
To me this is a chiddush. While certainly a hole or tear that touches a letter which occured after kesivah is not possul because the letter was mukaf gvil at the time of the kesivah. That is a straight out din is S"A. But in the case above, is he misunderstanding this halacha?