What steps will reproduce the problem?

Please see posts starting at http://reboot.pro/topic/16429-easy2boot-development-discussion/page-29#entry185728

Basically, it seems some loaders (syslinux) can boot from a PBR even if the hidden-sectors at 001C in the PBR=0. However, grub4dos will refuse to boot from the PBR -> Error 43: The BPB hidden_sectors should not be zero for a hard-disk partition boot sector

using --raw or --force does not help - you still get Error 43. Also tried geometry --sync and errorcheck off.

What is the expected output? What do you see instead?

Error 43: The BPB hidden_sectors should not be zero for a hard-disk partition boot sector

Suggest that if errorcheck off then it allows you to boot anyway?

What version of the product are you using? On what operating system?

Please provide any additional information below.

Can you explain why the solution works? i.e. why chainloader (hd0,1)+0x50 works but chainloader (hd0,1)+1 does not even when the PBR hidden-sectors value is fixed?

chainloader (hd0,1)+2 works. It seems that the OP made the drive in a strange way however...