Offer recommendations in an email

Dear experts,

could anyone explain the situation that we are having - offers from offer recommendation block in an email are seldom in a mixed sequence.

What I mean is that if we check offer recommendation "preview", we see offers sorted by ranking with most relevant on top. When we send an email, we take top 20 offers, but the sorting is opposite than it was in the offer recommendation "preview".

In the offer recommendation "preview":

Rank 1 - Offer A
Rank 2 - Offer B
Rank 3 - Offer C
Rank 4 - Offer D

When we send out an email, we get:
Offer D
Offer C
Offer B
Offer A

As I said it is not always the same. For some customers sequence is correct, for some - incorrect.