OK,
I see there is an issue here, and I found an old thread that seems to be similar issue. Even though that thread was closed as revolved this seems to be very much like it.
It seems that any expression that has \ in it is not rendered. The ones that don't are fine. Example
https://prntscr.com/xrnofh
As you can see in the rendered question
https://prnt.sc/xrnscu the ones that do not have \ in them are rendered fine.
There is an old thread that mentions that the \ are stripped when saving the data due to some thing to do with json data. the thread is here
https://wplms.io/support/forums/topic/latex-2/ Am wondering if this is related. Please advise.