BDY,
Do you have the speed-stir?
This time of year cold water will effect the cell's ability to have an accurate reading.
That said, I suspect your Taylor salt test is off.. You don't keep adding drops until the color stops changing (Like other tests) but the first change that does not change back is where you stop. It is not the color, but the change that counts.
In my opinion 4000 is too high. Not too high for the cell, too high for your taste buds. I try to run where the actual salt level is 3000 to 3400.
Salt cells make chlorine gas... It just does not stay in a gas form for very long.
Thanks,
Jim R.