iMessage glitch after adding legacy contact

We have spent a total of 3+ hours between texting apple support, Genius Bar, phone calls with apple support over this issue. My husband and I got new iPhone 16 pro/pro max a week ago. After inviting him to be my legacy contact iMessage has been bugging where it’ll change between his email and phone number. Some of my texts will literally show up in his email inbox not in his actual messages app. I’ll send a text to his contact (with just his phone number in the contact), it’ll then create a separate thread and send it to his email using iMessage while the original outgoing text will either disappear from our texts from his contact thread or it’ll just continue to show that it’s sending…. If I try to delete the thread with his email, it’ll just pop right back up in my message threads.

When I tell you we have done everything except factory reset, we’ve done everything. I’m hoping someone out there has had a similar issue and figured out a permanent fix or has some crazy idea that’ll help fix this mess. I already submitted a bug report to apple support but I doubt my issue will be addressed lol.

ETA: spent another 2 hours on the phone with apple support after erasing my entire phone twice. It was still happening. Then they realized after speaking with engineers it’s a bug on the latest 18.1 update… which is good news that it’ll get fixed but they couldn’t figure that out before hand??