My wife sometimes does not receive my text messages
Doesn't matter if I send from my iPhone or my Mac, she doesn't receive the messages until she sends one to me first and I reply to that.
I think this could possibly be related to the fact that I have her Apple ID email address stored in her contact information and it's somehow using iCloud instead of SMS? I also have her contact information in Outlook and Google, so she's a linked contact.
Naturally, I wouldn't block my wife :)
I am using an iPhone 13 Pro Max and she is using an iPhone 11 Pro Max and also her iMac M1 (messages are not received on either device).
iPhone 11 Pro Max