WTF can't they keep the time consistent two weeks in a row??

Simple.
Because it is the unacceptable face of fantasy and genre television.
They have fewer viewers than the acceptable face of fantasy such as soap operas and programmes that require your vote.
And of course, fewer viewers than sports programmes.

For years the BBC has treated the genre and its fans with disdain, being prepared to cancel or postpone a programme in favour of the acceptable.