I noticed that too but saw no tip damage last time I had a close look - it usually has to be fairly severe damage to kill the meristem. Interestly, cacti that display monstrose growth also often have that slight corky look in places. That's a shame David, maybe outside in the ground in zone 10 is pushing it a little, I believe zone 9 is where they originate. Try a pot maybe or more shade? I've found mine tough, like all Euphorbias really. Even a bad case of sunburn, which left nearly a third of it dead, couldn't kill it. That's the male plant btw. Female flower's different.

Like the green house it looks like the one I just got off ebay, to replace a smaller one, there great for growing cactus, epi and orchids plus so many other plants, I have a few months to go before I can get mine set up with 4ft of snow on the ground

As I understand it, the monstrose generally refers to the leaves being contorted or not resembling the parent plant. In the case of cacti, they will look as though they were made of clay and someone pinched them into a new shape...so hard to explain. Crest forms are, generally speaking, a wide stem base which will in turn carry more plant growth along the top (if it has leaves). Some plants are both... This is an example of a crested Dandelion that I found in my yard a couple years ago...

Here it is. I copied it from the internet for my own files. I don't know what species it is. I've misplaced the other. When I looked up "blind form cactus", I couldn't find any information. Thanks.