Why is my MacBook Air shutting off with charged battery?

I have a Macbook Air that has recently begun to shut down with a charged battery.

This always occurs just after it’s been closed and in sleep mode for at least a few hours - I open the display, have about 30 seconds of function, then the computer fully shuts down as if the battery is dead.

It will not turn back on unless it is plugged in, and when it does turn back on I see that I have anywhere from 20-50% battery charge.

I have already reset my SMC and it has not helped. It is now occurring every time I pick up my charged mac that has been in SLEEP MODE and open it when it is not plugged in.

My mac has all original parts, I have never had any problems with it prior to this beginning a few weeks ago. Recently updated to Mojave operating system (about 2 weeks prior to this beginning). No other charging issues or operating issues that I’ve noticed.

Thank you for any suggestions you are able to offer!!

Edit: Image added by request

Edit: Battery status after full night of charging with computer off

Edit: Battery status after 30 minutes of being unplugged from charger. Not sure if it’s important, but the charge shown here (~93%) does not match up with the charge noted in the status bar of my computer (98%).