Yeaaaaaaaaaaa. I'm not sure what the deal is. It shouldn't be a compatibility issue with any of the hardware I have in this machine.
Supermicro X10 board, I've tried the install with my HBA unplugged. i've tried different USB drives... just doesn't make sense.
I've been testing OMV with a bunch of different hardware the last month using OMV 4.1.3.
No issues writing the installation files on any combination of hardware, EXCEPT a Supermicro board (X9DBL-iF) with a USB Flash drive as the installation target. For that, I get the exact same error message as you. I've tried this with multiple flash drives on both the internal USB "A" and on the back I/O, always the same "failed to partition..." error.
I haven't tried OMV3.x on it, but was able to install 4.1.3 onto an SSD.