I thought it was a fungal or other infection invading through the pruning cuts into the stems, so I decided to clean and sterilize my shears every time I move on to another plant. In the third time used a different pruning approach: I did clean my tools, but I did not cut back all the stems. I left one stem with two branches intact. No pruning. All other stems have died back to the main trunk, but to my surprise, the die-back seems to stop here and the two unpruned branches are green. My conclusion is, it has something to do with axillary buds. Most of the time, this kind of pruning works, but often it does not. I have already lost one angel and I would have lost the other unique (unlabeled) hybrid if I pruned all the branches. Others, such as P. Sidioides have been heavily pruned and reduced to twigs, which re-sprouted and look like in day they were bought (just bigger).

I find this article: http://mybrokengarden.blogspot.co.il/2011/06/minimising-die-back-when-cutting-back.html

What is your experience about finding where to cut? Can you always see the presence or lack of dormant buds?