Thunderbolt to Firewire 800 external drive problems

I recently upgraded from a MacBook Pro 17" early 2011 to a MacBook Pro Retina 15" (early 2013). I have a Drobo and two Seagate 4TB external drives, all connected via Firewire 800. So, I added a Thunderbolt to Firewire 800 adapter and, it seemed, life was good.

I keep my large iTunes Movie and TV show collection on the Drobo. Since transitioning to the new MacBook, I have had a number of issue with watching movies on my Apple TV 3. Randomly, and periodically, the movie appears to be corrupted - the audio track skips/loops and the image is horrible macroblocked, as if the file is damaged. When I check the movies on the Drobo, opening it with Quicktime on the MBP, it plays just fine at the same spot it appeared damaged on the Apple TV 3.

A second symptom is this: I can no longer re-encode video with Handbrake with the source and target files on the Drobo - it gets some portion of the way through and it just stops, leaving the video partially encoded; again, at random locations/offsets into the video and not the same spot twice.

My initial thought is that connection to the Drobo is dropping out and coming back, on its own, but long enough to cause the above problems.

Is anyone else seeing this issue or something related when using the Thunderbolt to Firewire 800 adapter with large drives?

Thanks, in advance.