The charge pump not being stable can mean several things. If it’s not where it should be (it won’t be) the high side fets won’t turn on all the way, causing loads of excess heat inside the chip. This also may never recover, depending on the duty cycle, and then that chip will burn up/let the smoke out.

Essentially, the charge pump capacitor has a set of circuitry that brings it low, lets it get 5 or 12v, then floats it up to the voltage rail, to turn on the fet hard. If it’s only partially in, the fet has a resistance that is too high.