I would think this would be something that IP SLA would be perfect for. You could run some SLA operations on the access level switches at your remote sites and see if you're experiencing any issues. Solarwinds has a free tool for that which will allow you to watch, in real time, operations but you won't get any historical logging or data. Otherwise, you could always run a trial version of VNQM, setup some operations, and setup some alerts.
It also might be worth throwing a few access level ports into NPM to poll them for issues - maybe on a few ports that are connected to devices that users have complained about recently.