Replaced battery, slow charge and shuts off randomly

Hi, I recently replaced the battery in my 2012 Macbook Pro 15”. I followed the guide installation and properly calibrated the battery. Since installing it two days ago, it has randomly shut off three times and has been very slow to charge (only pulling 5-10 watts). I have reset the SMC and PRAM. I’ve also cleaned the magsafe port and cable (of which I’ve tried two). Is this battery defective or is there something else I can try?