The miner / coinbase value returned for Rinkeby blocks is incorrect. It appears to be returning the clique mining beneficiary derived from the extra data, rather than the usual 0x00 value.
For example, on block 9170727, the value should be
0x0000000000000000000000000000000000000000 but is returned as
One downstream effect of this is that client side block hash calculations are incorrect. For block 9170727, the incorrect coinbase causes the hash to be calculated as
0x697f02fdcf9b9c325664cedc77343236859967e147c34549295124df5fcb8f83 instead of
See this Github issue for more information regarding the miner value for Rinkeby blocks.