I tried copying the 99-sx.rules file into /lib/udev/rules.d instead and ran the reload rules command, but no such luck. I still get a lot of libsub IO errors. I tried deleting the 99-sx.rules file from /etc/udev/rules.d just to make sure they weren't somehow interfering with each other, but still nothing. I'll be looking into libusb to see if I can get more information about the error for troubleshooting. If you have any more suggestions they would be greatly appreciated!