I don't know that situation #1 is even possible... According to my understanding of PCM, it will either hold the last good frame of data in the transmission, or it will travel to some predefined servo location upon losing the signal. To go into a full on snap roll in fail safe, either the surfaces would need to be preprogrammed to do so by the pilot (which may be dangerous, and very unlikely), or the user would command it to do a snap roll at 150 mph just before the lockout occurred (which is also pretty unlikely)... It sounds like you're assuming a PCM system will react to a glitch like an FM unit will, with random fluctuations at times. Someone will surely correct me if I'm wrong, but I don't believe the system will react like this.

Kelly