Why repair the filesystem first while you anyway overwrite the whole storage device then?   /dev/sdb1 suggests an USB SD-card adaptor is used. Both the adaptor, which translates USB protocol into MMC commands, and the SD-card itself, which also does internal block managing, can mess up the filesystem. Not as long as this is plugged into the computer where the imager (or dd) is running, but once removed and put into the SBC, power is lost and re-applied. The USB + SD-card hardware (an