When the SPI Master Mode starts up, the boot ROM sets it to use 8-bit mode and uses a register called SPI_RWC to count the data it receives. This register can only handle up to 64KB of data. If too much data is sent, it should be split into smaller blocks of 64KB each. But instead of setting the count to 64KB, it erroneously sets it to 0, causing the SPI port to stop working and the boot process comes to a halt.
To fix this, you can use a setting called -MaxBlockSize switch 0xFFFC when creating the loader file. This limits the block size to less than 64KB.
Please refer the anomaly "16000047 - SPI Master Boot Fails When Block Payload Size Exceeds 65,532 Bytes" for more information in the below link.
https://www.analog.com/media/en/dsp-documentation/integrated-circuit-anomalies/ADSP-BF60x-anomaly.pdf#page=15