question

What battery?

Maybe the internal BMS is blocking the charger current?

Can you test the charger on another battery?

What is the battery voltage when tested with a separate meter when absorption is indicated?

What are you using to identify the battery as "only half full"

How is the charger connected to the battery? Are all connections of high quality and properly torqued if applicable?

This is behaving like excessive voltage drop.

Does the charger reported voltage in VC agree with the source reporting the 13.127V?

What settings are in the charger battery, absorption etc.?

There is a resistance between the charger and the battery - wires, connections, fuses, breakers, etc.

The resistance induces a drop in voltage from the source (charger) to the load (battery). The higher the resistance, the bigger the drop.

Pushing 11.5A to a battery at 13.2V through a low quality connection might mean the charger "sees" 14.2V and enters absorption and tapers current.

Example:

a) short 8awg wire with ring terminals security torqued to the battery terminals = very low voltage drop.

b) long 12awg wire with alligator clips clipped to the battery terminals = very large voltage drop.

The b) situation could cause the behavior you're describing.

Not sure why would would not pass charge through the shunt. Great way to make the shunt worthless from an accuracy standpoint.

Are the terminals tight?

This is really simple, and you seem resistant to collecting data. If the charger "sees" 14.2V due to voltage drop, and it's reporting that it's in absorption, then there's likely nothing wrong with the charger. There's something wrong between the charger and the battery.

Changing settings to Li-ion may have reduced the absorption voltage and caused the charger to trigger absorption sooner.

Did you try my settings?

I recommend you:

Disconnect, inspect and reinstall ALL connections between charger and battery. Make sure they are properly seated/torqued.

Change settings to those I recommended above.