iMessage photo not sending / freezing (until hard reset)

I upgraded to a iPhone 12 Pro (using iOS 14.3) and seem to have an ongoing issue that solves itself when I do a hard reset (but then occurs again some time later). 

Occasionally, when attaching a photo taken with the phone (from my photo library) to iMessage, it doesn’t send and I get a failed to send error message. The photo looks likes its sending and the blue status bar appears to freeze at the 90% mark for ages (see photo), until the error message occurs. I have adequate Wi-Fi and 4g – tried it over both. The users I am sending to are message users and connected to data.

If I do a hard reset, then resend the photo sends almost immediately.

I have checked my settings, tried turning I message on and off yet nothing seems to resolve it.

This is very frustrating - anyone else experienced this and know of a permanent

resolution or what the cause is?

Thanks