ADV7280M I2P flicker


I'm using the ADV7280-M connected to an IMX6Q processor over MIPI CSI2. I can successfully receive an interlaced video stream in the imx and display it cleanly but I would like to use the I2P in the ADV7280M.

I've enabled the I2P with

MAIN WRITE &0xFD : 0x84 // Set VPP Map Address
VPP WRITE &0xA3 : 0x00 // ADI Required Write
VPP WRITE &0x5B : 0x00 // Advanced Timing Enable
VPP WRITE &0x55 : 0x80 // Enable I2P

Although I see the deinterlaced video, there is a noticeable flicker. It is especially visible when setting the boundary box test pattern (write &0x14 : 0x07) - see attached output capture. Can the deinterlacer be configured to improve this?

Thank you for your advice