When pedaling, I feel a rumbling or vibration through the pedals. I am using a Shimano 105 Di2 groupset. The front derailleur is on the small chainring and the rear derailleur is in the 5th cog (I also tested the 4th). I replaced the original Shimano 105 chain with an Ultegra chain and tested Zwift Cog indexing across positions 1 through 10. The issue persists in all cases.
Here is a video demonstrating the problem (the rumbling is only audible when using headphones):
Yesterday, I received a replacement unit from support, and the exact same issue is present. How is this possible? Many users report the same problem, and there appears to be no solution. Is this a design flaw?