Strange happenings PBP and 12F683

[RussMartin]

Here's an example of one of many different attempts.

When the flag is 1, it works just fine.

When the flag is 0, it works fine when there is no data present (the first byte read is $FF). As long as the switch is held down, it flashes the LED one way; when it is released, the LED goes back to its "idle" condition.

For any other data present, it sometimes seems to go directly to PLEXIT; other times, it works as it should.

In fact, I'm playing with it now. On one attempt (with data present), it seems to jump directly to PLEXIT; on the next, it plays back the data. Then the cycle starts over again: One wrong response, one correct one. Time after time.