UCC27524: VDD Pin Over voltage risk

Part Number: UCC27524

Hi Guys

we can see our UCC27524 VDD voltage range max is 20V. If we have tested the voltage sometimes will go to 21V for <20nS. Even we capture the waveform for almost one whole day at 45C temperature, we just find one time trigger waveform. So do you think there is any risk to damege our device? So if we have 10ns over voltage, what the maximum VDD voltage level we can support?

Actually, we have found some device VDD pin resistance is about 70k ohm to GND.（normal part is about 80k ohm） Do you think this device is failed?

Thanks

-Pengfei