Using the Corona 7 Release Candidate - and it seems to have broken UVW randomisation.
One material, multiple maps (although the issue is apparent with just two maps) - both with identical UWV randomisation, in this case by Mesh Element - same seed, same values.
I seem to remember this making the randomisation match on different map channels - so the diffuse / bump / displace / whatever would be coherently randomised across the model - but this doesn't seem to be the case currently, each map is randomised differently making UVW randomise useless if you have more than one map in a material.
Hopefully a straightforward fix to return to the previous function? Nice.