A sofer was writting R"T tefillin and didn't leave 9 oisios at the end of "v'haya im shamo'ah" (in the shel yad.)
In Mishnas HaSofer from R' Yaakov Meir Stern (Siman 26 Sif-Katan 15) he writes that by R"T this isn't m'acev b'dieved. In Note 18 he is m'tzian the following teshuvas: Noda B'Yehuda Tinyana Siman 5, Shut R' Chaim Kohen Rappaport Siman 1, Shoel U'Mashiv Mahadurah Kammah Chelek Beis SIman 30 and Remah (רמ"ע) Siman 37.
The question is are the poskim l'maseh makil in this?
Obviously I'm assuming the sofer would have to tell the koneh however maybe he could sell these tefillin for cheaper if the original buyer wouldn't want them.
R' Shammai was asked this shailo and told the sofer that it's a problem (i.e. pasul), however after someone mentioned to him the makilim that R' Yaakov Meir Stern brings down he said he didn't know or perhaps didn't remember there were makilim. However I didn't hear that the psak had changed or not.