Hi Juan ,
just tried it on a quick test and all looked good . I could see the triangle groups

. There does seem to be some issues with swapping between the groups in that panel though (seems stuck on the first selected when you hit click the material , you can't then click on another material under the triangle groups panel). But it is now workable as I was able to put new materials on those individual groups, so many thanks!
I have made a post about hdri's,and mxi's as opacity masks causing a separate bug which is still present in this new build you can not currently use them as a mask and if you try they cause render errors. 16 bit files do work just not 32bit.
Anyway many thanks and appreciation for your prompt resolution of the triangle groups bug !
best regards