12v Accessory Battery issue

did some checking via the dash computer 3 flashes of the headlights to get to the lite diagnostic mode...
Got to the battery screen and it shows 12.1 volts, 12.3 ... hit the power button to get into accessory mode again and it dropped to 11.6 with a/c on full blast, put foot on brake and started up the car it shot up to 14 v.
did this whole thing twice... and the digital clock never lost track of time.

Some other noticed issues: digital clock didn't keep correct time, prior to this test, informed by my wife about that.
a sure sign something is going on...

Went ahead and swapped out the battery in the key fob, a week ago. When car would not start at all.
After that key fob battery was replaced - all was well, car started up, etc.

The following error codes were pulled with techstream about 3 days ago.

The 12v accessory battery was purchased April 2020.
Seems like a very short lifespan with below average amount of driving annually.

Before I replace it, anything else I should diagnose?
Techstream pulled the following error codes:
B1421 ( solar thing, don't care)
B1806 ( airbag squib),
B1816 ( airbag squib),
B1271 ( combination meter gateway communication error) - probably because of the replaced dash lights and I have not swapped out the resistor that is known to fail on this)

B2271 - IGNITION HOLD MONITOR

Thanks in advance.