i8355 from SDK-85 flakey [SOLVED]

Well, we can put a bow on this one now. I've found the problem. Turns out there was a damaged via on pin 40 of A15 (the optional ROM location) that provides +5 to pin 8 of A14 (the monitor ROM socket). The result was that pin 8 was floating. Pin 8 of 8355 or 8755 is I/OR- and is not used in this design (as I/OM- and RD- are used instead) and so needs to be tied high. With it floating, it was randomly gating an I/O read onto the bus I suppose. When I was freezing the part, I was obviously changing the switch point and causing it to mostly be high instead of sitting at or below threshold. The via was likely damaged when they made mods to the board for the Philips logic analyzer demo application. So, now both the 8355 and the 8755A work. Nothing sinister going on _inside_ the devices after all ;-) Thanks to all for playing along.