I also posted something related in the tech support forum but wanted to know if anyone else is also experiencing this issue.

I put 3 purple item grenade modes into the grinder hoping to pop out a legendary. Going off this list :http://borderlands.wikia.com/wiki/Grinder I should be guaranteed as long as I feed it moonstones…but it wont allow me… I have 480 stones so I definitely have enough, Ive tried going offline, and other methods but I still do not get the option to moonstone grind…,

I didn’t realize that was a glitch. anytime I put in 3 purples or 3 legendary’s I don’t get the moonstone option.

On the ps3, before The Handsome Collection came out, three purples with moonstones made the game crash. They had a patch and it took out the option to use moonstones with 3 purples. So don’t know if that has anything to do with it.

(just throwin’ that out there)