BMPCC dropping frames on ProRes, not RAW

Hi All!
I borrowed a Pocket cam from a friend awhile back to shoot a wedding, and it performed wonderfully. He came to me for a camera recommendation awhile back, and I sent him in the pocket route, and made sure he bought all approved media.

The night before the wedding when I was getting equipment ready and packed, I decided I wanted to try out one of my own cards and see what kind of performance I could get out of it. The card in question was a 16GB PNY class 10. http://www.amazon.com/PNY-Elite-Performance-Speed-Class/dp/B00DX5D49S/ref=sr_1_1?ie=UTF8&qid=1434506155&sr=8-1&keywords=pny+16gb

I did a fresh format in camera, and I was able to record ProRes proxy just fine, and then all of the other flavors of ProRes would drop frames after short durations of time. But here's the kicker though. I switched it over to RAW, and I was able to record with absolutely no issue. I could record a few clips of ProRes, have dropped frames, and then switch right over to RAW and have it run beautifully. I went all the way up to around 5 min clips, and I still didn't have a single dropped frame.

Is this just some crazy anomaly, or is there something to explain why this happens?

The SD cards tested and recommended by BMD are listed here:
https://www.blackmagicdesign.com/support/faq/43083

Results can be very unpredictable if you use cards other than those listed above.

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1. It looks strange. RAW is much faster. Maybe the problem is that PRORES is more computationally intensive?
2. Class 10 is irrelevant, you will be assimilated You should look at U-class. UHS-1 (1 in U letter) means that the card can support up to 10 MBytes/sec non-stop write ONLY. U3 nominally means that it can support 30 MBytes/sec write and it's enough for PRORES (Read: It's worthy a try, but does not mean it is guaranteed to work).

I have a following policy: I ask a seller whether it supports 30 MB/s write. If he answers "Yes" - I ask him whether he can return my money if it does not. If he answers "Yes" - I buy it and test it on site. EVERY ONE test ever failed on everything except Sandisk 95 MB/s. Disclaimer: I live in Russia, your consumer laws can differ.

I've even found a good reliable card that keeps pace with Prores HQ 25 fps, which is OK for lections aso, but I needed at least Prores 30 fps, so I exchanged it to Sandisk with 4 times less size...