I grow all my Oncidiums mounted and they seem to thrive despite my neglect. Frequent watering is definitely what they like--not necessarily lots of water at one time but some water more often. The pseudobulbs look rather wrinkled since I don't water as often as I should but they don't fail to bloom regularly except for one that's mounted on a branch of my persimmon tree, possibly due to inadequate light. Which is weird since it's probably the only orchid that I can't seem to kill (and I've had my share of them!!!). I even find old bulbs I have meant to toss sprouting new growth just sitting on my potting table.

So maybe we all have our "problem orchids". But good luck with yours; you probably just need to find the right mix of its likes and dislikes.