If it takes too long to load the EFI binaries, that might be BIOS setup issue. Have you tried other filesystems except FAT32 for the EFI partition? I’ve had luck with just FAT (FAT16) on some rigs that just refused to read FAT32 (still don’t know why).
Also, make sure the drives are in AHCI mode. Though this is mostly the default nowadays, I’ve seen weird BIOSes that defaulted to IDE mode.
If it takes too long to load the EFI binaries, that might be BIOS setup issue. Have you tried other filesystems except FAT32 for the EFI partition? I’ve had luck with just FAT (FAT16) on some rigs that just refused to read FAT32 (still don’t know why).
Also, make sure the drives are in AHCI mode. Though this is mostly the default nowadays, I’ve seen weird BIOSes that defaulted to IDE mode.