The "Implausible..." message isn't related to any actual error, it's just an informational message based on an assessment of how the latest sample relates to the previous one. To be honest, it probably doesn't serve any useful purpose, and it may be a bad assessment anyway. It doesn't relate to the subsequent "Unable to login..." message.
I presume that you paused recording manually because of the "Implausible..." messages? If so, the issue here is that, after a pause, it fails to login the first time. I can't think of a reasonable explanation for this, other than some quirk of the relationship between the program and the modem.