Can't get LTC4350 to share current

EDIT : Moved here as advised by the European Customer Interaction Centre.Any help will really be appreciated 

Hi everyone,

My setup is as follows:

The nominal output voltage of the system should be 12V.

The LT4350 Turns on when the output voltage of the LT3757 goes above 11.18V (UV).

The overvoltage will trigger when the output voltage of the LT3757 goes above 13V.

The gain resistor is calculated : 

Rgain = (Vcc-1.5)*1k/(Rsense*Imax)

Rgain = (12-1.5)*1k/(1m*4) = 2625000

Comp1 is 1n as per datasheet

Comp2 was determined by following the process in the datasheet but by simulation (step from 1A to 4A):

Which gives the resistor and capacitor combination of 150 ohm and 3.3u

status is pulled high to 3.3V and never goes down to show a fault.

The feedback pin of the ltc4350 is set to be 1.22V when the output is 12V

The feedback pin of the lt3757 is connected to the Iout pin which should provide a deviation of 300 mV (Rset/Rout = 0.3)

The LT3757 is set to output less than the nominal voltage of 12V.

The bottom LT3757 is set to 11.7V and the top LT3757 is set to 11.85V. 

I'm then expecting the LTC4350 to push these voltages up to 12V.

Here you can see the output of the share bus in Red. The gain pin of the top LTC4350 is shown in green and the gain pin of the bottom ltc4350 is shown in blue. It seems that they initially follow the same trajectory and then diverge.

Here is my project:


Any help will be appreciated as I have gone through the datasheet, looked at the example and tried multiple configurations.

Thanks in advance for any help!

Added information to why I'm posting here
[edited by: EngJunkie at 1:51 PM (GMT -4) on 17 Sep 2021]

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