@alastairstevenson ,
Great, Thank you
That hadn't occurred to me.
@mikeynags
I changed the lens from a 2.8mm to 6mm.
The 6mm was shorter by a fraction but I guess it did not have to be screwed in as far as the 2.8mm.
The glass did not crack right away. it actually happened days later, I guess the pressure of the end of the lens on it finally forced it to crack.