Download Coconut Battery on your Mac and add some screenshots to your question, thus we may be able to see some additional technical figures. However that seems to me another faulty battery, there seem to be quite a bit in the market with such percentage jumps issue and hibernation not working at all.
I’m having a similar issue, but I don’t think it’s the battery. At least not the battery cells. I recently replaced my battery using an IFIXIT battery. I starting seeing the problem you’re describing, rapid drop in displayed battery charge, with my old battery. The Apple diagnostics indicated my old battery was ready for replacement, so I assumed the battery charge was actually dropping that quickly due to a failing battery. However, I’ve seen that happen with my new battery as well.
So, it sucks to say this on the iFixit forum but… I got a battery off Amazon and it seems to be working fine. Got 3 hrs of editing on it and it went just fine. No sudden drops etc. Havent tested internet browsing etc but all seems regular. Will report back in a bit with more testing. All in all I can say that it was not a motherboard issue, it wasn’t related to any repair mishaps or else. Simply a bad battery (well.. two fo them).
I’m not convinced it’s a battery issue. I’m on my second new battery, reset SMC, calibrated on both and same thing - suddenly goes from like 70% down to 7%. Activity Monitor shows Google Helper using a lot of CPU resources so I’m wondering if it’s a software issue.