What type of control is it?
If it's an integrated device, chances are, an overly large value will slow down the response, requiring different compensation components -- if external compensation is even provided. It may simply oscillate if it's an internally compensated type.
This is typical of all controllers, whether average current mode, peak current mode, voltage mode or what.
Peak current mode controllers have the added difficulty of inherent chaotic instability at low ripple settings. Slope compensation (in essence, mixing voltage mode PWM with peak current mode to extend the stable range) helps, but only incrementally. This only works down to about 25% ripple, IIRC; any lower requires too much slope compensation to be practical, and it goes unstable again.
Tim