You obviously like to teach your partners.
Wrong. I don't like it at all. It is the 2nd worst thing I could do in class.
If you really think that your partner is doing wrong, and you feel so benevolently compelled to correct his technique, when it's your turn to be Nage, just do the technique as correctly and as slowly as possible, and your partner will learn it from your action better than from your words.
This only works if your partner has an eye for subtle changes.
Or better call the Sensei and ask him if the technique is correct or not, and he will be very happy to explain it to both of you.
Here in America, nobody likes a tattletale.
If you don't believe me, perhaps you would believe Osensei.
Who has spent all their time training with O'Sensei's method?
Who has reached O'Sensei's level, by following his training method?