My hubby always reports anything acidic as tasting "bitter", it could be from dissolved CO2 as well.
My recommendation is next time you "test" it, pour a glass and let it sit at room temperature for a while. See if lots of bubbles form on the sides of the glass. If so, then you'll know degassing is your problem... and perhaps agitating a glassful (or bottleful if you're careful!) might "flatten" it by releasing some of the CO2 that might be causing it to taste acidic and sparkling.
And hey, if that doesn't help, you could always cut it with some more nectar when you drink it, then at least you'd have the flavour...
"The main ingredient needed is 'time' followed closely by 'patience'." - The Bishop 2013
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