It’s an issue specific to IOS 14. I’ve never had an Apple Watch, iPad , MAC or anything other Apple device other than an iPhone and the issue still randomly occurs. It first appeared when I installed iOS 14 on my IPhone-X. I upgraded to the IPhone 12 Pro Max and the issue persists.
Now for clarity sakes, I’m referencing ONLY sms/iMessage. This post has nothing to do with any other messaging or notification app/service (WhatsApp, etc). You can rebuild from a fresh iOS 14 load but most users here who have tried that have experienced temporary relief as the bugs eventually return.
The only work-around that has proven useful is the kill the messaging app after every text, sent OR received. It’s an awful and inconvenient work-around but it works.
[Edited by Moderator]