Measurement accuracy issues on XR – Welltory: Heart Rate Monitor Review

Maybe it's the phone, but I've done development with basic heart rate sensors before, and for whatever reason the signal from my finger is always super clear - way more pronounced than most. Even so, I've tried Welltory measurements repeatedly - sitting, lying down, relaxing, pressing, arms in various positions - and I can't get better accuracy than 90% and it tells me there's a problem. I thought it might be an XR issue, but another HRV app I've tried (HRV4Fitness) doesn't have this issue - optimal signal quality from them. They also show the real waveform, which makes it easy to see that they're getting accurate measurements. Whereas with Welltory, the event spikes (not the real waveform) don't line up with my actual heartbeat, especially with small rate increases caused by breathing. All of the stats and integrations look great - measurement just seems terrible even on the same hardware. Might try it on Android later (those stats do look nice) but will leave the review low on here for now.
Review by StartupSam on Welltory: Heart Rate Monitor.