I just sent a note to Canon support about this but I want to see if anyone else has noticed.
I've set up my 1Dx to record RAW images on Card 1 (a 32GB UDMA card) and .jpg images on Card 2 (a slower 16GB card.)
During one prior outing I noticed that, after downloading everything, the count of RAW images was lower than the count of .jpgs by one. I didn't really go beyond noticing since I was busy on other tasks.
I was out yesterday, however, and after downloading everything I noticed that my RAW count was two lower than the .JPG count.
I scanned through the images and figured out that there were, in fact, two missing RAW images.
Nothing had changed with camera settings along the way.
Prior to setting it up this way everything matched so there appears to be something a bit buggy with how images are split amongst cards.
Has anyone else seen anything like this?