TVP5150: TVP5151 Register to detect the lock state are not updating properly

Hi,

 We have the tvp5151 chip as a decoder connected to the  analog video input. We need to support both PAL and NTSC standard videos . To detect the hot plug events  we used  the the Register1 and Interrupt Status Register A.   Below are the observation

1.Lock interrupt(bit 7) of Interrupt Status Register A not updating for any of the lock transition
2.Lock state interrupt (bit 8) of  Interrupt Status Register A is not updating during NTSC /PAL  video input  change
3.Lost lock bit (bit 5) in the Reg 1 is not properly update when we  change the video inputs (NTSC/PAL)

So none of the above bits are not showing a proper lock state , when changing the video inputs between PAL and NTSC type. Did  we miss some configurations to get the lock state properly on this registers? How can we detect the lock state change properly from tvp5151.