collect() computes sqrt((x - last_x)^2 + (y - last_y)^2) against the position recorded on the previous poll and overwrites last_x_/last_y_ with the current one — it never accumulates into a sum. A stationary robot reports 0.0 every poll; a robot that moved 3 m since the last poll reports 3.0 once, then 0.0 again once it stops. The Measurement's own name and its schema's "description": "Total distance traveled in meters" both suggest a running total, but that's misleading given what the code actually does. This is a known issue, still unfixed and unrenamed.

onConfigure() declares a transform_tolerance parameter (default 0.1) but then reads back transform_timeout — a name that was never declared — into the member this Measurement actually uses. rclcpp's get_parameter(name, out) silently no-ops on an undeclared name rather than throwing, so neither key you might set in YAML reaches the TF lookup: transform_tolerance is declared but never read, and transform_timeout is read but never declared. The member is left uninitialized (float transform_timeout_;, no default), so the TF-lookup timeout actually used at runtime is whatever that memory happened to contain, not the 0.1 shown above. Known, tracked in dc_measurements/plugins/measurements/distance_traveled.cpp, not yet fixed.