That's good news but a pain to figure out which item in the system is the one causing issue.Apogee has done several tests on my units, including running frequency sweeps through both units as well as each unit individually at 96k for an uninterrupted 10 hours per test. No components tested faulty, no dropouts occurred on their system, and there were no indications of any problems whatsoever. They're sending the units back to me. They've suggested that there might be something in my OS that's not cooperating with the interfaces and think that a good course of action would be to do a ground-up clean install of everything on my machine. Not using any backups except for files, just wiping the machine, reinstalling the OS and manually reinstalling all of the programs. This is doable, albeit time consuming.
I'm going to do some testing when they're back before going to the effort of an OS wipe. I've requested a letter from Apogee to be included with the interfaces when they send them back that states that the interfaces have been into their lab and have passed all tests, and have been given a clean bill of health. Just in case I have to sell the interfaces and then the next owner has the same problem. This might give them some leverage in making an extended warranty claim.
To recap, you had bought the Apogee quartet?