Last week, I replaced the battery on my 11” mid 2012 MacBook Air. I charged it completely, then used it on battery power until it shut off, then left it for 5+ hours as is recommended for calibration. The battery is still dying after 2-3 hours and the % left is not accurate (eg it will go from 45% or so down to 7% and then sit at 7% for a while. It has gone down quickly to 7% specifically multiple times.)

I did try calibrating it again and reset the SMC but I haven’t noticed any improvement. Is there something I’m missing?