Vibration in the pedals when in under load?

I watched your video and have exactly the same issue (except I have it in 3-4 highest cog gears). Did replacing the freehub help?

Also, seems lots of people have this issue with the 11-28T Ultegra, anyone try a different cassette?

Same here 11-28T Ultegra and I get vibrations in the smallest/fastest 4 cogs. Garmin sent me a new freehub, but that did not change anything. I tried the installing the two washers behind the freehub to get a setup that is closer to my bike (thru axle), but with the spacers the freehub blocks in reverse, so maybe my neo has a problem.

Getting a feeling that the vibration / gnarly torque profile is related to the electromagnetic drive of the Neo itself. I observed it is more pronounced when in downhill / active drive mode when pedaling so overlaying Neo's motor drive with pedal input seems a culprit. Other than that it is NOT related to once per pedal revolution NOR to once per NEO disc rev, only to certain combinations of load and rpm (and this is pbly why it is easier to generate in the smallest cogs, it seems unrelated to specific cogs to me...). Didn't have it on an Elite Direto XR so it must be the way Tacx has implemented the direct drive hardware OR software or both. :-(

PS: My cassette is a Dura Ace 11-28T, tried chain replacement, likewise both chainrings 50/34 in front. Didn't change anything...

What I really don't understand: Any electro magnetic brake (or motor) can generate an almost perfectly smooth torque profile by adjusting the windings in the stator (or rotor, depending which side is which) accordingly. Having a finite number of magnets (and there is MANY inside the Neo 2T flywheel) does NOT mean we have to accept a torque ripple of this magnitude - it can be perfectly smoothed out by design. Look at a motorcycle induction brake, for instance...

I stay by my assumption that either hardware or software design is flawed, or both.

I replaced the Neo 2T unit for a new unit and the issue is still there. For some reason, this trainer has a design issue with my configuration (10 speed, ultegra 6700, 11-28T cassette with 2 spacers). Garmin support was not very useful advising on this.

I've had a Neo 2T for about 6 months and have exactly the same experience.  From what I can remember of my physics education (which was quite a few years ago) I think it's a situation where the resonant frequency of the drive train matches that of the Neo.

One thing that is interesting to me in your description is that you have a a set up very similar to me - in fact identical (same 10 speed, same cassette size, same 2 spacers) except mine is 105 vs Ultegra.  This got me thinking that maybe the problem is down to a specific drivetrain setup that has the characteristics that match a resonant frequency. 

Given that there are lot of happy users out there it would be interesting to know if there are any common themes in the setup for those of us who do experience this,  For everyone who is following this thread and are experiencing the problem, what drivetrain have you got (10 or 11 speed, rear cassette size and number of teeth on the gear you feel it and ideally how many links in your chain)?  If there is a common factor then we can work out what we need to change....the more who are able to share their set up the more chance we have of finding the common theme.

Interesting -  many seem to have 10-speed 11-28, however resonance (if it is) seems to show up on many different cogs, in my case at least on 11, 12, 13 and 14t cogs. Crank has 50/34, had 50/36 on before, no difference. Changed chain length by 2 links, no difference.

I've tried an 11-speed R7000 12-25 and/or 5800 same setup. Front is a 50/34.

The vibration feeling is faster but less severe on the big front cog but that makes the trainer twice as loud also

I have the same problem with a very similar cassette (10 speeds, 12-28). The vibration in the pedals is very annoying. Did someone find a solution?