lkrn command line issues

I was trying the lkrn command-line on some different hardware than I
normally use, and I'm seeing some issues.  I seem to just get jibberish
instead of the command-line that I passed in:

cmdline_phys: 99000
cmdline_user: 80b28f90
cmdline_user len: 2
cmdline[0]: 0x13 ""
cmdline[1]: 0x00 ""

It seems limited to one system.  The command-line still works on some
other systems and in QEMU virtual machines.  I checked to see if it was
a regression, and found out that lkrn command-line support has never
worked on this hardware.  I tried loading from both "legacy" GRUB and
GRUB2, but they have the same failure mode.  Any thoughts on how to
debug this further?