Frame drop in 3 * 2 MIPI lane configuration

Hi Everyone,
I am facing packet drop issue in 3 * 2 lane configuration for below specification.
3 * 2 lane configuration.
Frames per second : 800
Frame width : 32K
1 sensor : 4VC
total character device : 12
When am reading data using V4l2 API, there is a random frame drop. But there is no frame drop for 1 * 2(total character driver 4) configuration. I have assigned separate cpu for each sensor but packet drop is not solved.

         I have a doubt that why there is a packet drop when am reading 3 sensor data in parallel. I am running thread in max priority(FIFO) and each thread running in separate cpu.

        please can anyone give some suggestion where the issue is.

Thanks for your time.