I ran this too on mine, I had the mode set to memmap. Badram is old, grub these days expects memmap.

There were a few areas but they were close enough, so this is what I ended with.

Blocks of 64K were enough to fix this.

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash memmap=64K\\\$0x3c8f0000,64K\\\$0x49068000,96K\\\$0xa24660000"