McIntosh C2700 Right Channel Issue

Bought a brand new C2700 preamp from an authorized dealer back at the end of June. Sounding great so far but just last night developed an issue where the right channel does not engage (play music) until around 20-40 seconds into the first song after the tube warmup process has finished. Also, the right output level meter does not move during these 20-40 seconds. Tried a couple of different inputs (USB, Optical 1), with headphones, and through my (also new) MC275 with same results. Seems like once those 20-40 seconds has passed, everything is good to go. And yes, I have tried various songs that I know have both left and right channels. 

McIntosh Support first recommended doing a factory reset which I have done but still encountered the issue tonight. Next thing recommended was swapping tubes (have not done yet).

Has anyone else run into this issue on the 2700 or past models? If so, what was the problem and how did you resolve it?

Thanks!