1° difference should be ok. I'm working on a theory or an idea about what the moon really is. For the idea to be true, a near perfect vertical rise of the moon could not occur in reality.
Does anyone claim that a vertical moonrise does happen? Given the geometry of the earth-moon system, I doubt that it is possible.
Earth-Moon Image
Actually, it is possible - at least very close - in certain circumstances.
When observed from a point on the earth's equator, the celestial equator goes from the horizon due east or west of the observer vertically to the zenith. Any celestial object on the celestial equator would appear to rise straight up from due east, pass directly overhead, and set vertically due west. If the moon were exactly on the celestial equator, it would do so. Since the moon is on an inclined orbit, it crosses, but doesn't stay on, the celestial equator twice each orbit. Because it doesn't stay on the equator, it wont track
perfectly vertically. Over the 6-hour period from rise to culmination, it will drift about 1° in declination. It might be closer to vertical than that if you're about 1° north or south of the equator, depending on whether the moon is at its ascending or descending node; I need to think about that.
If you have stellarium or a similar planetarium program, set your location for latitude 0°, longitude E 59° 24' 55" and date & time 2017/03/13 15:02:48 (UTC), and center the view with east in the middle left to right. The moon should be just rising directly east, then go straight up and drift slightly to the south.