Does it mean anything if ipod (6th gen) doesn't beep when bootloader installed?

[Frankenpod]

Having a lot of trouble getting another flash-modded ipod to work.  I assume everyone is tired of people asking for help with flash mods, as it's not a specific rockbox issue.  But this one is weird, and I'm not sure if it's the ipod logic board, the memory card, or something else at fault.

Essentially I can get it all up and running in OF mode, but RB's bootloader doesn't seem to be able to 'see' the iFlash (if I boot into RB it gives an ATI -large negative number error, that I have come to associate with the drive being missing entirely).
I was thinking it was a bad, or oddly-incompatible, memory card, but as I've now found all the components seem to work when I put them in a different ipod, I suspect it's a problem with the particular ipod logic board, rather than the memory cards or a usual flash-mod issue.

  The thing that I noticed is that, unlike on every other ipod I've installed RB on, there's no "beep" when the bootloader is installed.

Is it possible the bootloader is not getting correctly written or that there's something wrong with the memory that the bootloader is supposed to be written to?  Does the bootloader live on a part of the main storage, or is there some flash memory somewhere on the logic board where it resides?  (The bootloader is already present from a previous rockboxing of that ipod, but I'm starting to suspect it's somehow corrupt, and isn't getting overwritten when I try to reinstall it).