Replaced Battery, % Now Inconsistent, Coconut Batt says "Failure- yes"

I replaced the swollen OEM battery in my MBP 2012 with one from ifixit. However, since doing so, the few times I’ve had to use it away from a power source, the battery percentage drops immediately from 100% to 94% and then falls quickly until the MBP goes into hibernation at around 40% - I might get slightly over 2 hours use out of it.

I’ve tried the SMC reset listed here: https://ifixit-eu-en.helpscoutdocs.com/a.... No joy.

I’ve installed and run Coconut Battery, which says “Battery Failure - Yes” amongst other things (I will try to attach the screenshot)

Is there anything I can do? Or do I have a dud battery and need to replace it again?

Thanks,

David

Coconut battery screenshot: