LT8228 question regarding V1 (high side) CSA stability


I have a problem with a custom board designed using the LT8228 and stability of the V1 CSA.

With no stability capacitor fitted (C12 in the section below) I cannot get the LT8228 to remain in operation.
It will start switching and then shut down after a few cycles, investigation has lead me to the V1 CSA as a possible issue.

If I fit a 3300pF capacitor on C12 the issue is resolved and the LT8228 will start and run consistently, however my Imon1 pin then goes to 2V preventing full operation of the device.

My question is:

If a stability capacitor is fitted to the CSA1 or CSA2 input;
a) what typical value should it be?
b) what other consequences or changes may be required to IMON1 or ISET1P pins?

Intended operation is for a bi-directional battery charger with a 48-55V battery range on the high side and 24-36V battery on the low side.

Many Thanks