If a mezzuzah fell and a non Jewish employee put it back up
Theoretically is there an obligation to take it down and put it up by a Jew? (With a bracha?)
Or is it kosher the way it is?
This video (after 1'30") reports a similar question was asked to R Yosef Shalom Eliashiv who brought a Maharam Shick that it was allowed for a non-Jew to put up a mezuza if a person is old/sick and can't do it himself. He argues the mitzva is to have a mezuza not to put it on.
However, others (the Sdei Chemed, R Shmuel Wosner) argue that putting up the mezuza has to be lishma, for its own sake, which only a Jew can do.
Since it is a dispute, R Eliashiv ruled that, for the sake of resolving the doubt, it was better for a Jew to rehang the mezuza (e.g., removing a nail then setting it back).
As always, be sure to ask a rabbi in any specific case.