Are you getting good clock from the bnc cable? Try playing the adats without timecode to make sure you have good digital lock. If you hear clicks and pops, go over all your bnc connections. Don't just jiggle em, unplug and reinsert each one. Sometimes even tho it's plugged in doesn't mean you have a solid connection. BNC is kinda fucked like that - not the greatest interlocking mechanism devised by man - and in the digital world, that lock is all important. Especially check the bnc connection on your adat bridge. I find that in multiple converter setups, it is cleaner to use bnc "T" adapters to feed all the sync in's instead of chaining thru the boxes.

Also, you might have better luck slaving the BRC to both external wordclock and smpte position generated from the USD, instead of slaving PT to LTC from the BRC. If you do it this way, remember to shoot a little bit of code at the top, then stop and give the adat's time to shuttle before you start again. I would give at least 15-20 seconds preroll for the ADAT's to sync up.

Hope that helps.