SFMC Send SMS from JB with no phone in DE

Question

I have a case when SFMC JB performed an SMS send to records, that did not have a phone number in DE for Entry Source, but there is a phone number assigned to them in the database.

The Journey settings were set to "Use phone number attribute from entry source - Phone".

Here is an example record in DE:

SubscriberKey | Email | Phone

123 | example@gmail.com | null

Help states that "To send SMS from a journey, the normalized phone number (country code + phone number with no dashes or parentheses) is required in your data extension."

Could you please tell me how to troubleshoot this case, or if you see any other potential things that have given the following output? And how to perform a send so it does not happen again?

Thanks a lot!