A modular device, that includes an operation event log in respective modules of the device to record time-stamped events, e.g., errors, and a configuration log in a central controller to keep track of changing configurations due to swapping or removal of modules. A controller updates the configuration log each time a module is added to or removed from the device. Log information may be stored locally with the device or in a remote server accessible via a network to facilitate remote diagnostics. To assist in diagnostics, the disclosed method includes merging the configuration and events logs in a way to display log entries according to a selected configuration where errors in current modules are demarcated. The apparatus includes routines in the controller to effect retrieval, processing, and display of demarcated events according to a selected configuration.