Messages in iMessage are not loading for certain contacts on iPhone

Certain contact messages aren't loading. Only a select few of my connects randomly start “typing” once I select them and it will not show past messages and will show loading on the top. I have restarted my phone multiple times turned messages off and so on nothing has worked and it has been months of this glitch. It is annoying because now I cannot view texts from these people because they disappear once I read them once or reply. Any help?

[Re-Titled by Moderator]