The replacement battery in my older MacBook Pro (Retina, 15-inch, Mid 2014) is failing. It is not yet overheating or...

First of all, my technical abilities are not up to those of the others on this thread. I just want to share some observations, largely anecdotal. I started having random shutdowns coincident with battery going well beyond duty cycles and it’s max charge capacity falling distinctly. Screen goes dark. I plug in power cord and press power button repeatedly. Eventually system restores as it was at shutdown. There is no indication that the OS recognized a shutdown. “Normal service is resumed.” Seems to happen [?only?] on battery power. Generally with battery in a mid-range of discharge, Always happens at or very shortly after boot or rousing from long sleep. My subjective notion is that in attempting to reload a bunch of stuff it demands more peak than the battery has to offer. I’ve had none of the horizontal bar issues. I’m going to replace the battery and see if that changes anything.