I have not gad this problem until a month or so. I take them all the time, almost daily of grandson. Want to share with family. Did a setting get changed?
Welcome to Android Central! When you send a video via text message (i.e., as an MMS message), it gets compressed, since the maximum filesize for attachments is about 1 MB. This is a pretty small file, and a video will lose a lot of detail. It's better to upload the video privately to your Google Photos or YouTube account, then share the link with the recipient.