TL;DR - cautionary tale of the plagued Charge 3. Fitbit doesn't seem to really have any software solutions that can help with flawed hardware. The model is a liability to the company and I'm surprised it is still available for purchase. Replacement offerings should include the Charge 4 (in hopes that lessons were learned in developing the updated model).
My first Charge 3 developed the horizontal black line problem. Fitbit provided a replacement Charge 3. A few months later there are many problems with the replacement.
First it was a battery drain issue. No changes were made in usage, but suddenly my unit went from getting 6 or 7 days to complete drain in 24 hours. I did the always-recommended reset procedure with no improvement. I actually did that several times with no results. Fitbit then told me I should disable most of the useful functions and do a battery test (i.e. make it less useful and see if it lasts).
I did another reset, but then couldn't sync with the app, the unit wouldn't measure heart rate, and it had a black line in the middle of the screen. My hopes were dashed that the problems with the original unit was an issue of early release hardware.
I deleted the unit from the app and paired it again, which solved the sync problem, but the other issues persisted. Battery and/or firmware issues were apparent when the battery indicator dropped 5% right after placing it in the charger.
I'm not sure which issue triggered Fitbit to propose another replacement (free Charge 3 or 50% off a new device (including a Charge 3?!)), but I figured 3rd try's the charm. TBH, I don't expect much, but I can't bring myself to spend money on another fitbit model.
The latest issues came after the replacement offer. Aside from the screen lines, it seemed that the battery and heart rate problems were gone after some battery cycles, but then the screen went blank, the unit wasn't found by the app, and LEDs weren't lit/flashing on the back. The only sign of life was vibration when pressing the button. Holding the button would prompt a long vibration followed by several short vibrations. The reset procedure had to be tried several times before any response (loading bar and then smiley face). Heart rate would then come back after charging for a while, followed by sync with the app. I have gone through this three times in the past 36 hours and noticed that my unit now has three black lines.
Currently, the heart rate reading is 66 bpm, but there is no LED activity on the back of the unit. The Charge 3 saga continues...
Hopefully the quality control for the Charge 4 was a lot better. Maybe Fitbit will eventually offer it as replacement for those with unresolveable Charge 3 issues, which I expect to have with my next unit.
