Appending measures uses 4/4 time signature
In a new file, set the time signature to 6/8. Append 2 measures, then the last one has 4/4 signature in its properties.
In Score::insertMeasure, InsertRemoveMeasures::insertMeasures is called before setTimeSig is which adds the default time signature of 4/4 into the TimeSigMap. This is then used as the time signature for the next appended measure.
Adding a call to fixTicks at the end of Score::insertMeasure seems to fix it.