Why did my "goat cheese espuma" flop?

I recently got myself an iSi Creative Whip and have been having a lot of fun playing around with it. Tonight I tried one of iSi's recipes, which uses the following ingredients:

• 250 g goat cheese
• 125 g sour cream
• 125 mL cream
• 1-2 tbsp olive oil

Preparation is basically to purée the goat cheese, sour cream, and oil, mix in the cream, strain it through a sieve, load it into the whipper, then charge and cool it.

At the denouement, I was greeted with a brief but ominous fizzle followed by an even briefer splatter of yogurt-like liquid, very much like the explosion of snot one witnesses after somebody sneezes a little too hard. After clearing the cheese blobs from my shirt and hair, I proceeded to scrape the remains (which was in fact the majority of what went in there to begin with) with a rubber spatula and spread it on some crisp toast; it was delicious in spite of not even being remotely close to an espuma.

I'm well aware, as the manual makes sure to mention about half a dozen times, that the whipper will fail to perform any actual whipping if the fluid inside is too thick or viscous. I was quite skeptical myself, before charging it in the first place, but until now I haven't really tested the limits of this thing, and I figured, if I was able to strain it through the sieve (with much mashing, I might add) then it would be whippable.

So I already know, superficially, why this failed, but that only leads me to a deeper why which I have been unable to answer myself: Why did this happen with one of iSi's own recipes, found in the very recipe book that is included in the same box as the whipper itself? I have to assume that iSi knows what they're doing and it was me that screwed up; but how? What did I do wrong and how could I have fixed it?

Some possible avenues of investigation:

• There are a great many different types of goat cheese available; I used the standard soft/unripened type, but there are also goat cheese "spreads" that are probably less rich. Perhaps the recipe was actually referring to one of these?

• I used ordinary (14%) sour cream; perhaps the fat content was too high and the recipe intended for light or even fat-free sour cream?

• I had a lot of trouble actually puréeing the mixture; using a blender, I found that the mixture didn't really move around much, so I had to keep scraping it back into the center so that it would hit the blade. The recipe actually says to use a blender or food processor but I assumed that a blender would be better. Should I have used a food processor instead, or maybe even a stick blender? Would any of this have actually made any difference, given that the consistency of the final mixture was very smooth (albeit thick)?

Are any of these likely to be the root cause? Is there anything else I might be overlooking?