Tried render and save - didn't fix issue
Check Sequence - no issues detected
Note: I did both of above
before posting previous comment. I've learnt lots from @keithsw1111 but the biggest is to do the 2 things above before posting a question/issue

Turned out issue was somehow I'd saved and rendered as Master View, when I saved as my view (Christmas 2017) issue was fixed, except for 1 sequence. I've posted a new thread in the Bug section on this one.
So I was correct, I had done something dumb.
