Sudden drop in battery capacity and sudden shutdowns

Hey everybody!

I'm having a little problem with my 2017 13" MacBook Air running

OSX 10.14. It shuts itself off at 30-40 percent of battery charge

without any notification whatsoever. I've been monitoring the battery

health of my laptop with CoconutBattery and what it shows me is really

weird. Its capacity dropped from 64% to 38% in one month, even though I

was using my device as usual. Also there's a low charge cycle difference

too. I've calibrated the battery (charge for 2 hours, drain, let it sit

for a few hours and then recharge it again) three times already and the

issue doesn't go away. I've reset the SMC too. I'm pretty sure it has

something to do with the component giving the battery info to the OS.

Because I booted Windows with Bootcamp and the battery percentage also

jumped 10% or more in a minute.

Is this a common issue? Do you have any idea what could be wrong?

Thank you for the replies in advance.

Here is the reading of CoconutBattery from the last few months: