Old story.. Zwift and Kickr Core resistance solved (for me)

I, and many others, have complained in the past about the resistance when using a Kickr Core at 0% gradient on Zwift. It happened using an Apple TV, and was just the same on PC. I was always using the Wahoo Fitness app in workout mode to add resistance while riding on Zwift in order to have a realistic feel and range of gears. The resistance sent by Zwift at 0% (using Bluetooth) is unrealistic and much too low.
Sick of slow and unreliable connection using Bluetooth on my PC, this week, I tried an ANT+ USB stick (Garmin) , and apart from the very fast connection at startup, the resistance at 0% is fairly close to normal!
Why is there a difference in resistance between Bluetooth and ANT+ ?
Is Wahoo or Zwift at fault with this problem?
I suspect the fault is in the Zwift program …

You may find the answer in an article on Zwiftinsider (can’t link to it in a reply). Search for WAHOO KICKR TESTS: CONNECTING VIA LEGACY ANT+, ANT+ FE-C, AND BLUETOOTH:

" We headed out to Fuego Flats, turned our Trainer Difficulty down to 0, and rode for a minute or more at a steady cadence of 90 without shifting. We did this for each of the three connection methods. Here’s what we found:

** ANT+ (non FE-C): 184 watts average*
** ANT+ FE-C: 215 watts average*
** Bluetooth: 182 watts average"*

ANT+ FE-C uses a higher base resistance than Bluetooth or normal ANT+.

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Bear in mind that that Zwift Insider article is 18 months old.

Wahoo recently added (via firmware updates) Bluetooth FTMS support to the Kickr, which had been missing before. On 1 June 2021 they added that to the Kickr Core too. See KICKR CORE Firmware Updates – Wahoo Fitness Support

So it’s worth checking your firmware is up to date.

@ Steve
My firmware is always updated!
Past firmware changes to date have never resolved this problem using Bluetooth (on any platform) on Zwift.

I have , as always, updated my Kickr Core firmware.
I updated my Zwift app to the latest (15/6/21)
My resistance at 0% gradient is now close to normal when using Bluetooth…
Why did it take so long to get it right , Zwift…?