Poor pulse oximetry accuracy.

My wife has a vivosmart 4 and I recently got myself a fenix 6 (now software version 8.10) titanium sapphire and I've been comparing the pulse oximetry of the two devices on both of my wrists followed by my wife's wrists with a professional pulse oximeter and the vivosmart 4 is surprisingly often within 1% accuracy of the professional device. The fenix 6 on the other hand is usually underreading by >= 5% all the time. I'm aware this is not meant to be a medical grade device but the numbers it gives are so much less accurate than the much cheaper device my wife has, and the values are so low that they'd warrant hospital admission or professional sleep studies when they're not warranted. I would not normally pay much attention to the values it gives since they're meant to just be there for trends rather than accuracy, but the much cheaper device being far more accurate is a little disconcerting when they apparently use similar sensors. It hasn't improved in a week of usage. I've tried tightening and loosening the band and on both wrists but the issue persists. I've seen other people posting their oxygen saturations and they're often in the low 90s when healthy young people at normal atmospheric conditions should always be in the high 90s. Do you have any suggestions, or is there any effort being put to improve it? Thanks.