There's a window every three months for adjusting UTC (calculated time, based on cesium clocks etc.) to be aligned with GMT (Measured time, based on observations on earths rotation.
Some times, an additional second is added to UTC, other times, a second is subtracted from UTC, so that UTC, ideally, should never differ from GMT by more than 1 second.
This practice has been going on for many-many years. So I don't think that just the leap second in itself is to blame here.
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