[Suns-at-Home] Some old Suns stopping w/o keyboard?

[Peter]

I've got a few old SS10's lying around, and some of them exhibit the
following annoying behavior.

If you unplug the keyboard, it's equivalent to hitting stop-A -- you
get the monitor prompt.

If you replug the keyboard, you have to type "go" to resume.

But some of the SS10's don't do this.  They just keep merrily chugging
along without a keyboard.

Does anybody know why this is, or how I might convince the ornery
SS10's to keep on running without a keyboard?

Thanks!