Videos sent & recieved in Message are much smaller.

I've been having this problem recently, and I've checked my Message settings and have low quality off. My issue is, when receiving or sending videos to and from family members, who also are iPhone users, their videos are both low quality and about 2/3 the size of the video sent, meaning they will not fill my screen, about 2/3, if that. Some of my family members don't have this issue, I don't know why I am, but I was also told that my high-quality videos that I have sent, have been coming across the same way, to recipients. How do I fix this?

I do not want to upload to iCloud or any of that, I just want Message to work the way it should.

I am growing tired of having to tell people to bounce over to Facebook Messenger, to send my high-quality, full size videos.

Thanks in advance.