I had a similar, albeit even weirder situation.
I received a letter dated October 13, 2017 informing me I had missed my first test date, and this was my last chance to sit the test. Except I never received the first invitation, and there was no update to my ECAS.
A couple of weeks later there was a new line on my ECAS saying 'We sent you correspondence on October 24th, 2017' and thats it! No other updates other than the AOR and started processing.
I went for my test and everything went fine, although I have been stuck in process for almost a year since my test, and 18 months overall.