Why would my JB notification shade show SMS from over a year ago?

Running JB 4.3 on an old HTC OneX, this happened twice this month, first displaying (on the pull-down notification shade) a text from Dec. 2016 then again a text I'd received in Aug. 2016. Also had many buggy duplicate SMSs lately, like every text I receive twice, in real time then again 16 min. later. Any ideas SMS glitchiness could indicate, should I be checking for malware, or what settings could I toggle?

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