Hey @Gweeds ,
My sleeve (tattoo) does not go low enough to impact the sensor, but I do have dark arm hair that can cause some inconsistent readings if not trimmed. My experience is that the Sense 2 seems more susceptible to this than my previous Charge 5 device for some reason. But again with my experience, the Sense 2 seemingly provides me with better response to change in heart rate when doing intervals than the Charge 5.
Some devices react more to tattoos than others (even when made by the same company). From your post it sounds like you are past the return period, do you have have tattoos on both wrists that may interfere? If not, maybe change the wrist and also change the setting in the fitbit app settings (https://help.fitbit.com/articles/en_US/Help_article/1988.htm). If changing wrists is not an option, consider gifting(or selling) the device to a friend or relative as it will probably work for them (as long as they don't have a tattoo that could interfere). Then try something else before the return period expires.
Probably not the answer you want to hear, however this characteristic of the heart rate optical sensor that affects not just the Fitbit Sense 2 alone, but all optical HR sensors for all brands are affected by tattoos to varying degrees.
