Container exited unexpectedly - What does this error means?

Come on, you have to at least appreciate the dark humor (humour) in the error message. I think that's pretty nifty.

It's also nothing new - I vividly remember a similar period about two months ago where we all of a sudden got bombarded with these messages.  Most likely Microsoft have again messed around with the service without properly testing the changes.

Since you are on Premium, raise a ticket with Microsoft and ask them (nay, demand from them) to give you an explanation and an assurance that this will be fixed again.