Temporary Mezuzah

If one checks their mezuzah, do they need to put up another one in the interim?
Depends: If one will be checking their mezuzah right away and is actively working on getting it checked, he need not put one up in the meanwhile. If, however, one is concerned about the kashrus of his mezuzah and took it down and is waiting to get it checked (like in days of old that one would wait for a traveling scribe to pass through the village), it depends: if he owns the house, he should put one up; if he rents and it is outside the land of Israel, he could be lenient.
דעת קדושים (מבעל האשל אברהם) סי' רצ"א ס"ב
וכן נפסק בספר "חובת הדר" פ"א ס"ח
ועי' בספר עלי דשא (שפירא) סי' ל"ג עלה ט שדן בזה
See here

Slanted Mezuzah - Now No One Is Happy?!

A Jew affixes a mezuzah to the doors of his house. Most mezuzos you'll see are on a diagonal. This is due to a difference of opinion between Rashi and Rabbeinu Tam. One says that the mezuzah is to be place completely horizontally while the other claims it should be placed vertically. In order to satisfy both opinions we compromise and put it on a slant. (רמ"א יו"ד סי' רפ"ט ס"ו)
Now, if the opinion of Rashi is to affix the mezuzah vertically, and that of Rabbeinu Tam is to do so horizontally, placing the mezuzah at a slant (neither vertically nor horizontally) is contrary to both opinions and seemingly futile?!
There are two explanations offered: a. There is a third opinion in the Gemarah that if one places the mezuzah diagonally it's unanimously kosher. The argument is only if vertical or horizontal is also valid, but both opinions agree that diagonal is certainly good.
b. The chief opinion is indeed like Rashi who holds that it should be affixed vertically; however, Rashi would hold that diagonal is also considered like vertical. Now, when one puts it diagonally, he is technically not putting it completely vertical either, so Rabbeinu Tam would not outrightly object either. Thus, we place it so making both opinions "happy."
שו"ת מנחת אלעזר ח"א סי' ל"ו ד"ה וגם
See here