Random no power issue

[Hjoken]

I have a 2013 yaris hatchback (187k miles)I've been having a odd issue with. Every once in awhile when you come out to start it ,it will be completely dead power wise like the battery is disconnected. If you jump the car it starts right away and the issue will disappear for quite awhile. My wife uses it for work and on the way home stopped at target and it did it to her as well. I changed out the alternator last year thinking it might of been the issue. I tested the battery tonight and its showing 12.8v (on the terminals and the battery leads) and 14.2v at idle. I am thinking possible bad battery cell or possible cables? Figured I would ask instead of throwing parts at it.

Thanks in advance for any advice.