DS90UB964-Q1: Video stream received but losing LOCK with line length and count change detected

High Speed Interface Team:

We have the quad deserializer 964 with 4 cameras + 913 serializers in trigger mode with coax cables. Sensor active resolution is set to 1280 x 960 at ~10 FPS. We're seeing the video stream over the CSI-2 output but are encountering a few issues:

1.  LOCK is lost intermittently on all RX ports. LOCK_STS and PORT_STS will almost always read back as 1 but that the lock status has been changed since last read. This is during camera operation (triggering). 

2.  LINE_LENGTH_CHG and LINE_CNT_CHG are also detected every frame. When we read back the line length and line count they consistent at 1920 x 964 (correct for our resolution in bytes + 2 embedded status lines). Is this likely related to the losing lock problem?

3.  BIST mode run from the deserializer only works and PASSES (0 errors) with an internal clock source setting of 01 (75 MHz). PCLK and 37.5 MHz fail with 255 BIST error count. Our PCLK runs at 74.25 MHZ so we are not sure why this mode would fail (see below)

3a.  Possibly related to the BIST problem: We are NOT seeing a continuous PCLK. It's only valid shortly before each frame through the duration of the line valid, then turns off. Is this potentially a problem for the lock circuit or BIST mode?

Thanks for the help.

Regards,
Ryan