The use case is:

-Contacts are entering into the journey when an event occurs in Sales Cloud, with their email address correctly.

-When contacts come to email activity, it seems that they have received the email.

-When we see the tracking, we can see that emails are not sending to all contacts that are entering.

Anyone know how to solve this problem?

UPDATED:

@Markus: It seems ok, here there is the email activity history of today for this journey:

@Eliot: the subscriber are active in all subs list, and the email was validated with the synch sendable data extension. I have tested this journey every time, and every 10 first sends works, but after that, do not send more.

Note: There were some ampscript rules were trying to render empty fields (such as ContentBlocksbyID rendering the name in the subject). I am going to avoid that in order to check if it is works finally.

Thanks for your support.