it might be because she is taking him off you, i'd just put him on the floor and always say the same phrase before you go, i still do this with rich at 11 and he used to say it back now he too cool, although i did get love you this morning.
but if its her, then i'd have a word with manager too
just saw your update post.
then i'd see how it goes, but he could only be crying for the couple of minutes he is taken from you. to be honest i'd say that was bad practice and try just letting him go in himself, he seems ok this week to do it with a stranger, so its not the nursery it could be just the thought of being taken