Don't know if this F10BT method can apply to F930BT, files can be different.
You get very strange signs with dir behind, you mean that directories names are non-standard characters ? Perhaps caused by a transfer interruption, reading/writing errors or damaged sectors in NAND memory.
Care, i'm not a specialist.
Before upgrade my USER\SYSTEM\Download\ folder was empty, i would try to copy and erase these strange elements, then try to restart navi or upgrade.If it's a NAND failure perhaps there is the relevant test tool in the Super testmode but these sensitive functions are not recommended.