KM11 uPB question

Hey folks, While working on my 11/45, I built up a KM11 replica based on Tom Uban's ExpressPCB layout. I noticed the following behavior when trying to use it in uPB mode on my KB11-A CPU: * If I set up uPB, set KM11 S1 on and S2 off, and resume execution, the breakpoint fails to stop the processor * BUT, if I depress and *hold* CONT, while it is held down the CPU will be held in T2 on the target microword * If I then reach over and flip on S2 before releasing CONT I can hold the machine there in T2 Documentation on the KM11 seems to imply that the machine should just stop at the target state holding in T2 without having to do the holding-down-CONT-while-flipping-on-S2 thing. I was wondering if this was an oddity of my KM11, my CPU, or is that just the way uPB mode works on these things? thanks, --FritzM.