When you perform a private transaction with te correctly specified gas limit of 23,176 wei the private nodes get a root mismatch.
A private network with 4 nodes.
Deploy a contract to Node 1 and Node 2 with the gas limit of 24k
Node 3 and Node 4 will process the transaction correctly (the are not party to the private transaction)
Node 1 and Node 2 will fail with the error InvalidBlockException: Failed to import block: Invalid blockand Invalid block: receipts root mismatch
I suspect this is because the private transaction requires more gas and is somehow causing the gas used to be wrong.