Cannot load 'system.img' - Help please!

Hello all,
Support said I should try get some help here as they are not able to help with this…

I am in the middle of flashing my shield with a stock 7.2.2 rom but when I try to flash system.img using the command fastboot flash system system.img I get an error load_file: could not allocate 1701233852 bytes error: cannot load ‘system.img’

The bizarre thing is that if I unplug the OTG USB cable from the Shield box, I get the same message, which means the error is about the PC, not the Shield TV box!!
I have LOADS of space on my HD and 24gb or ram… so no issue there either. What could it be talking about?

Thanks,
Mark.

I also get this message, which does point to not enough space on the Shield TV box… so perhaps the first message shows when the cable is unplugged because it still cannot find enough space to install the system.img file as it is not connected to any space!

D:\Android\7.2.0recovery>fastboot flash vendor vendor.img
sending ‘vendor’ (544699 KB)…
FAILED (remote: data too large)
finished. total time: 0.024s