I am not sure any location fixes the issues to be honest. I thought I found the spot switching to Bicep but even that will just crash from one day to the next. I was pleased that the ECG/EKG and the BP insights seemed to work on the Bicep but the overall results seem spotting. I have just moved from right Bicep to left today but this is the last straw. So many problems and all we get is the device is loose, tighten. Any tighter and I will probably mess with my circulation.
The gold standard is the chest strap and I would accept some differences between wrist and bicep but I have maxed out at 207, which I am pretty sure I am not capable of at my age. I have seen my Garmin show max 138 but whoop 190/200’s. I have no experience of Whoop 4 but hear even those users say 5 is pitiful compared to it. My personal preference is to allow us to import HR for activities from Garmin/Strava etc that used a Cheat Strap. And while they are at it import Power, Distance, Cadence, GPS, Pace & Stride(runners) to give a much better picture of the effort than just HR and Time.
As I stated moving to the bicep seemed to work well at first and you might want to give it a go. Complain to Whoop and they will send you a free bicep band, at least they did with me. I do not moved the bands, it is now permanently on my bicep. It could be a hardware issue but fingers crossed it’s software that will be fixed with an update.
Here is my experience of Bicep.