Due to a problem in the Intel® FPGA Generic QUAD SPI Controller II version 18.1 , erase operations starting from sector 256 onwards will fail, causing all write operations to be unsuccessful when using a MT25QU01G flash device
Erase and write operation executed below sector 256 will be performed without problems.
This problem affects the Intel® FPGA Generic QUAD SPI Controller II included with the Intel® Quartus® Prime Standard Edition software version 18.1