During the PXE boot process, the entire process takes a long time, or the boot.sdi file fails to download properly.
GSS 3.3 RU 12
The TFTP block size for the subnet is too big
Set the multicast properties for TFTP/MFTP to 1456
NOTE: If this resolves the issue, you can try higher settings for the block size to see what works on the subnet. The higher the block size the faster the client will download files from the PXE representative. If the packet size is too large the file will have issues downloading