Commit 2d525e9a88 ("Testsuite: T9099: harden GRUB console-select navigation with expect() check") added expect() checks after each GRUB submenu transition in BOOTLOADERchooseSerialConsole(), but did not fix the underlying race it described: on the installed system, BOOTLOADER_LOAD_TMO (5s) is slept before the first KEY_DOWN is sent, while that system's top-level GRUB menu auto-boots its default entry after the same 5s with no margin.

Under host load the countdown could win, so GRUB booted straight past "Boot options" and the new child.expect('Select console type', ...) then blocked for the full BOOTLOADER_TMO waiting for text that would never appear.