Hi Jason,
I had a T752 which spent so much time in the repair shop over three separate issues I eventually lost my cool and demanded a swap-out. The Sydney NAD agent arranged for a T753 in place of my T752. Cool, all was going well until it was just out of warranty - now it has the same problem you describe.
I'm running it in the open with the lid off and working on isolating the fault. It appears to be heat related as it takes much longer to drop out when room temp is low, and above 25 deg C it occurs within 30 minutes. I was hoping it would be mechanical (dry solder) but I fear a dicky microprocessor. Further diagnosis will occur this week. Stay tuned.

Mike