Thanks, Below is the request received from pool, so if you check first header above which looks like big endian has previous hash as is.
It is not big endian.
I do not think that this is exactly what your miner received from the pool. I think what you are seeing is based on an internal representation of the data which makes it appear to be different than what it actually is.
So bloc header has previous hash flipped in 32 bit chunk ?
That is what is being displayed, but that is not what it actually has to be in the block header.
But as per documentation it doesn't say so.
Because your miner is displaying that information incorrectly.
prev_hash: da780ff935f3917ed99a7b616cb98ebb3104b3fa000b7acd0000000000000000
The correct block hash is f90f78da7e91f335617b9ad9bb8eb96cfab30431cd7a0b000000000000000000. You will notice that if you byteswap this so that it is actually in big endian, the block hash becomes 0000000000000000000b7acd3104b3fa6cb98ebbd99a7b6135f3917eda780ff9 which is an actual block that you look up on a block explorer or node. Looking up what your miner is displaying in both its original form and byteswapped form results in not being able to find such a block.