DS90UB960-Q1: Virtual channel number is different to what I expect

I have the 960 configured to send data from RX0 and 1 to MIPI port 0. I have only one camera plugged into RX1 and can capture video data in the FPGA I am using. But the issue I have is that the VC is comping up as 0 (I get 0x2b in the first byte of the short packet, as I amusing RAW10 data). I would expect that the VC should be 1 as I was under the impression that the 960 would re-map the incoming VC to the ones that are set in register 0x72. If I read 0x72 I get 0xe4 which suggests port RX1 should give VC-1.