I have a Garmin 235 and the heart rate monitoring also sucks. I think now it just stopped working but when I got it new it was sort of maybe accurate indoors when you're not moving. As soon as you go running or outdoors where sunlight can interact with the sensor it's basically useless, either measuring your cadence instead of your heart-rate or just producing total garbage. So I bought a polar chest strap which is incredibly reliable.
It's been a while since I looked at reviews but when I did the conclusion seemed to be all wrist based monitors are iffy and vary greatly from person to person. Maybe some people have a stronger signal at their wrist?
EDIT: I do like the watch though. Lightweight. Durable. Long battery life. Accurate GPS. Everything I need to track my running.
I've had the vivoactive 3, 645, Fenix 6, and now the 255. The HR sensor is much improved on the 255 (and similar generation models) compared to older models. It obtains accurate HR quickly and doesn't stray or go wild with readings. Enough so that I can go without my chest strap for most runs. I still use a chest strap for high HR interval runs, as it has gone wacky at times here. Another nice thing with the new HR sensor is it uses what seems like a glass cover over the sensor, unlike the plastic resin on older models that had a tendency to develop a spider web of cracks.
Another nice thing I've noticed with the 255 is GPS is normally super accurate, and I'm now able to rely on it 100% of the time for auto 1 mile lapping.
Well the 235 is nearly a decade old now, there has been much improvement in heart rate tracking since then. The 235 is as old as the original Apple Watch.
It's been a while since I looked at reviews but when I did the conclusion seemed to be all wrist based monitors are iffy and vary greatly from person to person. Maybe some people have a stronger signal at their wrist?
EDIT: I do like the watch though. Lightweight. Durable. Long battery life. Accurate GPS. Everything I need to track my running.