Whoop 5/MG has been awful on the wrist for me and I have well documented the problems. Bicep is better but still not great and needs to go back to the wrist for ECG/EKG and BP insights. Also HRV seems better on the wrist. Anyway I have given up on Whoop and will probably be a one and done subscription.
But Whoop early on sent me a gift certificate for being on the community a lot. I used it to get the Leather lux band but never thought much about using it, looks pretty but not ideal for working out or for me, cycling. Will get sweaty and probably fall apart pretty quickly.
Anyway since I am running down the days I decided to use it. But something strange has happened! My HR has suddenly become very accurate when cycling and the more I monitor it the closer it seems to be to my chest strap. Weather has been a bit crappy so only indoor cycling which is not perfect to test but the leather band seems way better. Why you ask? Well number one possibility is the band is not stretchy at all, so once in place stays very firm and can’t flex. So since it’s not flexible like the standard bands, might it not be affected by bouncing and vibrations and stays firm on the wrist. Maybe?
I just took out one of the my original 5 bands and it is very very flexible and when I say flexible you can easily pull it and inch or more longer. Compared to the Amazfit band, this has barely any stretch what so ever. Amazfit has been very good for HR. We already know the 5 band fades quickly did they also make it too flexible where it’s more affected by rapid movement or vibration. With the nylon strap even pulled tight I can easily get my fingers in between, this not possible with the leather band. Could this be why Whoop has been a problem?
I am totally blown away by this new finding, is it real or just another false dawn. I will monitor for the next few weeks but right now it’s 
FYI: Bicep band is also very flexible.
