Hi guys. I just received my zwift hub yesterday and did first ride. While riding steady at around 75rpm and changing to the easier gear my cadence drops down slowly to 60-40rpm and then comes back to where it should be. Is this fine or could be a problem? I did calibration multiple times. Also my chain is extremely loud at lower/harder gears (last 3) all others works fine I adjusted the cable. Any tips? Thank you for any help.
I donāt have a Hub trainer specifically. But if the game is trying to report your pedaling cadence, and the only information it has is the cadence at the rear wheel, then it has to extrapolate how fast your pedals are turning over from how fast the rear āwheelā is turning and how much power is being put in. (Havenāt thought about this before, so speculating here.)
From the perspective of whatever sensor is measuring RPM at the rear wheel (the Hub is effectively the rear wheel here), when you downshift at the same pedaling RPM, that sensor sees a drop in RPM. Youāve changed the gear ratio, so your 75 up front is now a lower RPM in back.
So what Iād guess is that the system then takes the dropped power into account and realizes that youāre still pedaling at the higher RPM. Iām guessing that thereās just a lag in calculating that. Iāll have to pay closer attention to my own, see if thatās happening with my H3.
The noisy gears likely indicates that your derailleur is misaligned a bit. Could be a bent der hanger, could just need a slight barrel adjuster turn, could need a bit of a b-screw adjustment. Calvin can help with that 
A mismatch in the wear-level between chain and cassette will cause a myriad of issues. (noise, poor indexing and shifting)
The best way to eliminate this as a possibility is to install the cassette from your bike wheel on the trainer. Alternately, get a new chain to go with the fresh cassette on the trainer.
More remote possibility: the cassette on the trainer may be out of spec. The ones included with the Hub are lower-end āSunraceā brand which are mostly fine but occasionally have quality control issues. (poor machining or alignment)
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Good call, definitely a possibility. Given that itās only on a few cogs and that der adjustment is easy, Iād try that first, but yeah, new chain or old cassette might do the trick too.