Do not cross-flash. A Dell DSL2520UZ2 has different I2C addresses for SGPIO (LEDs) than a Supermicro version. Flashing the wrong vendor's firmware will not brick the chip but will cause the PHYs to "rail" (stay open), generating massive heat. Compare the MD5 checksum before flashing.
SAS expanders are sensitive to voltage droop. If your drives are reading/writing during a flash, the 12V rail sags, and the expander undervolts during the write cycle. This corrupts the firmware 100% of the time. Always flash from a maintenance OS or bootable USB with zero disk I/O. dsl2520uz2 firmware hot