Hey Tom (and anyone else with Sentry3 Rails),
Fix for this one was in an earlier message > http://www.mail-archive.com/observium@observium.org/msg00519.html
Make sure you have the latest MIB and add the code to sentry3-mib.inc.php in …/observium/includes/discovery/sensors
Also, you were right about the graphs Tom – tweaked the cron jobs and all is well!