I have also experienced problems with clients using Transcend...
I know it is not what you want to hear, but you didn't come here for sweet talk;
If the SanDisk works, why use the Transcend? Time and time again, I use the SanDisk = camera works wonderfully. Use Transcend = problems. Weird stuff too, like working fine then suddenly issues. Put SanDisk in, no problems. My experience is that the extra cost for the SanDisk shows in the actual performance of the product, not just for show...Transcend could use a little more quality control so I could experience the same performance with their brand.
Please don't think this is a SanDisk commercial. Your experience may vary. But I get consistent performance out of using *any* version of SanDisk, even 4-year old Ultra 512MB cards. (I know, try not to laugh, they are in the emergency bag and get used when the big boys get full.)
My $0.02 worth; go with what works...the rest is up for debate over beer and wings.
FWIW, the Hasselblad uses a CF reader/writer that is designed for UDMA...
John