TPS74801: BIAS pin voltage is different before and after enable signal turns high

Part Number: TPS74801

Hi team,

May I have your help to check below question on TPS74801 BIAS pin voltage?

Customer pulls up BIAS pin to 12V by a 4.22k+4.7k ohm divider which makes BIAS pin equals to 6.3V.

This is already violated our spec in datasheet and I have already asked customer to modify.

But the question I would like to check is, why the BIAS voltage on the scope is different before and after enable signal turns high? (from below waveform, the BIAS from 6.2V to 4V after enable turns high, once enable turns low the BIAS will become 6.2V)

Thanks.

Regards,

Allen