Success! Thanks everyone for the suggestions and tips.
I did the green scrub thingy on brandnew mandrels, used the thinner mixture, air dried for two days, heated slowly and far away from the flame and made sure that the glass was hot and runny enough.
Result? I did 10 beads today, not even once did the release crack!
You guys rock ... thanks so much!!! Now I will have to do some more trial (and error?) because I can't use brandnew mandrels for the rest of my life