Hi,

I would like to mention what B.B. should have said about where to look for a battery drain.

You want to check between a removed negative battery cable with the ammeter.
Place it in between the battery negative post and cable. A drain of approximately 20 to 50 milliamperes.
A few LEDs worth is about normal with the cars alarms being off.
Any higher do what he suggests, look for something on.

The charging voltage seems to very normal.
A battery at 12.43 is about half empty. From there down, things can get very questionable fast.

Battery age effects cells individually.
As B.B. is saying, you may have a weak cell. Sulphate flaking shorts the bottom of the cells or a the lack of good electrolytes level in a cell cause low voltages.
Not all cells age or die equally.

The newest battery maintainers can double a battery life, if used consistently, to avoid internal discharging by their own nature.
I don’t like going over a week without float charging or driving.
But I have about ten batteries to stretch their lives out on.
A little float charge of 13.2V maximum with a minimum amperage can be endured to avoid fluid losses.

Same technique goes for a flashlight or hand torch.
One bad battery in a series stack kills a flashlight.
In this case you can check them all to find if you have only one being a culprit.

I have studied car batteries in the past, that had cap openings, by putting a probe right into the electrolyte and to a post or the next cell.
Back when they were tar topped a screw put down in them made them a six or nine volt source. A Handy cheat for my hand held six transistor radio.
Jeez I’m old 🥴

A bad cell will show more drop or an unevenness across a car battery.

A current loading or a 15 second cranking with a voltage bounce back up with in 30 seconds is the best for a better confirmation of its status of reliability.

Phil