TopicDiagnostic: "Timestamps too far in future seen" but timestamps are correct.

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I'm using a diagnostic_updater::TopicDiagnostic for a NavSatFix topic with the following parameters.

diagnostic_updater::FrequencyStatusParam freq_param(1.0, 1.0, 0.15, 10);
diagnostic_updater::TimeStampStatusParam time_param(0, 0.275);

And I frequently receive "Timestamps too far in future seen" messages in the rqt_runtime_monitor diagnostics. When the error occurs the earliest time stamp delay is always approximately -4.25 seconds. However, when I display the timestamp of the NavSatFix message in the terminal, it's the same as the UTC time for my computer, and there's no messages with future timestamps. What could be causing this?