problem with featured products

Hi, i have a block in the email customizer with 4 products (featured).
The website admin told me that the last days the products shown in the emails are not 4, sometimes are 3 and sometimes 2.
I did a check, i opened one of my orders made it processing and got the email. I then canceled it and made it again processing and got another email.
In one email the products are 3 and in the other are 2.
There are enough products set as featured.

Can you solve the problem?

best,