Vibration in the pedals when in under load?

Bearings fail in many ways, not always audible, I would definitely contact garmin support. Mine is a light vibration, mostly due to the magnets I can feel it most when I am waking the unit up, and goes away pretty much completely when I get up to speed. Does your change based on "wheel" speed, like when you shift into the higher gears?

The vibration is most obvious during the down motion when pedaling at low cadence, regardless of gear. At high cadence I feel it less because I'm spending less time in that part of the crank.

I've had the Neo 2T for just under two months. I only started feeling the vibration in the last week. It is quite noticeable on low cadence at 150W or higher. I usually feel it on the down stroke, but when I pedal in circles, i can feel it through a full crank rotation. I thought it was the chain, so I replaced that yesterday. No change. Checked the crank bearings. No problem there. The cassette is new. The chain rings are in good shape. I can feel the low frequency vibration created by the magnets when turned by hand, as expected, but that same low frequency vibration is also occurring at much higher RPMs.

I went through this experience. Replaced almost everything related to the drivetrain on the bike, including the bike and still felt the vibration. Went through about 2 months of back and forth with Garmin, including replacing the bearing, cleaning the unit, and the vibration was still there. Finally, Garmin was kind enough to replace my unit with a refurbished unit. Same issue. I'm now convinced, at least in my case, this is just how the unit feels and for whatever reason I've become much more sensitive to it.

That seems to be the only explanation that makes sense. One reason that I may have started noticing it more often now is that I have gotten into better shape after 5 years off the bike, and can now produce much higher watts on a continuous basis.

It is not normal at all to have vibrations in to the drivetrain . I have bought a couple of Flux S. One is doing it while the other is not. 
exactly what you are experiencing, under certain range of power and cadence, it keeps quiet. But if you try a sprint or a low cadence, it starts vibrating, like if the wheel is not aligned (unbalanced)

did anybody on this forum request warranty or replacement? This condition is not acceptable by any means!

thanks 

I was able to get a replacement from Garmin. Vibration was still there albeit slightly less. So maybe normal and very subjective.