If they want any paying at all, presumably they will.

They are required by TFL to have a working contactless and Chip'n'Pin device mounted in the customer compartment. I have a feeling we're talking about things that happened in the past.

What's required and reality are sometimes very different. I know I've been told the card machine doesn't work, then magically after saying I have no cash it'll start working a minute later...

Do TfL "mystery shop", they should and with confiscation of license and vehicle for malfeasants.

Yes, but their enforcement team is way too small for the number of taxis and private hires on the road for it to have much effect.