Sense wildly undercounting steps but after checking seems like I'm not alone

[sarcazm]

Initially I contacted CS a while back and they had me do a manual restart (hold the power button down 10 seconds, etc.) and walk 100 steps to recalibrate the device.  Also I switched to entering my calculated stride/step length and going with turning off the auto mode (and it is already on my non-dominant wrist, and I move my arms enough).  My Fitbit Sense is from Nov. 2020 so not a spring chicken but I take great care of it.  Still, I've contacted CS multiple times and they still tell me to keep restarting and recalibrating the device.  It is to the point where I am doing this at least 2-3 times a week, as the undercounting of steps is grossly inaccurate - I would need to be able to fly in order to get out of bed in the bedroom, go to the bathroom, go to the kitchen, and then sit down on the couch in the living room and complete that in 7 steps (just one example).

I'm curious how many people, if any, are experiencing THIS problem.  I am trying to determine if it is an issue with the age of the device and the hardware, or possibly something that needs a firmware update as the timing, for me anyway, seems to coincide with the update to OS 5.3 (44.128.6.12).  
  

[JohnnyRow]

1)  Stride length has nothing to do with step count.  It is used only to convert step count to distance.

2)  Walking and counting 100 steps does not do any "calibrating".  That is just a test to verify the accuracy.  What are your results when you try to 100 step (or preferable even more) test?  Does it seem fairly accurate then?

3)  In your example, those all seem fairly short walks.  I think sometimes short walks, say under 10 steps, get disregarded as they often are actually non-step arm motions.

4)  If you are willing to give up heart rate data for a day, a better test might be to leave it in your pocket for a typical day and check the day's step count, then compare that to the step count you typically get for a similar day, wearing it on wrist.  In pocket usually gives a more accurate step count; if you get similar daily step counts worn both ways, that is about the accuracy you can expect.  Nothing worn on wrist will give exact step count, and errors will seem more extreme when looking at short distances and short times, and tend to even out over longer time periods with more continuous walking.

[sarcazm]

If it converted step count to distance shouldn't they be close?  And what about GPS?  

Interestingly enough, after I go through the motions the CS people keep telling me to do, it DOES give me an accurate step count at 100.  It used to last much longer than only 2-3 days though - that is really the issue I'm having.  Like once a month or 2?  okay.  Every few days is getting ridiculous, IMO, and I question why it seems to keep lessening the step count without adjusting distance to match.  

I first had to contend with this issue due to my mobility aid and there being no adjustment for this and nothing planned either, so much of what I do has to be manual.  I will try the step count in the pocket thing, so thank you, but that still doesn't address the issue in question.