Unexpected Bootloader Interaction with rEFInd

[NX06]

Hello,

i recently constructed a dual boot image with Linux CentOS 7 and Memtest86 (Passmark).
The initial master image worked as intended with minimal input. I basically only added a grub boot entry for Passmarks .efi-file, but it works as intended.

After deploying this image via fog to 12 identical servers the servers’ grub entry for Passmark broke somewhat depending on what bootloaders are involved.

When booting directly from BIOS to disk (grub), then everything still works as intended.
But a problem arises when we PXE boot into the fog menu and exit with rEFInd to boot from disk.
rEFInd correctly boots into the grub boot loader that is configured on disk. grub in turn can then boot CentOS as normal but it cannot boot Passmarks .efi-file.
Error Message: “sector sizes of 1 bytes aren’t supported yet.”

When we then exit out from grub back into rEFInd, reFind can then boot any ondisk .efi-Files without issues.
Curiously when booting the standard grub fallback entry that is preconfigured from the CentOS installer via rEFInd and exit grub again into a reboot, then the entire problem vanishes permanently.

From then on there are no further boot problems regardless of what boot loaders are used and in what order. It does not matter whether passmarks efi-file has been loaded at any prior point. It only matters whether the grub centos fallback option has been loaded by rEFInd.

This behaviour is consistent over 12 identical servers and multiple reboots each.

Our FOG-Server is inside a VM so we can easily disconnect it to reboot into another ondisk OS to workaround this entire issue without manually handling each bootloader. And for our next image iteration i will try to swap out the ondisk grub for rEFInd and see if that brings any weird behaviour.

Do any of you know if there is any interaction between rEFInd and grub that might explain this behaviour?