datasketches-java: ArrayIndexOutOfBoundsException during serialization

Seeing this sporadically for FrequentItems:

java.lang.ArrayIndexOutOfBoundsException: 13
	at com.yahoo.sketches.frequencies.ReversePurgeItemHashMap.getActiveValues(ReversePurgeItemHashMap.java:180)
	at com.yahoo.sketches.frequencies.ItemsSketch.toByteArray(ItemsSketch.java:316)

as well as Quantiles:

java.lang.ArrayIndexOutOfBoundsException: null
	at java.lang.System.arraycopy(Native Method)
	at com.yahoo.sketches.quantiles.ItemsByteArrayImpl.combinedBufferToItemsArray(ItemsByteArrayImpl.java:104)
	at com.yahoo.sketches.quantiles.ItemsByteArrayImpl.toByteArray(ItemsByteArrayImpl.java:55)
	at com.yahoo.sketches.quantiles.ItemsSketch.toByteArray(ItemsSketch.java:471)
	at com.yahoo.sketches.quantiles.ItemsSketch.toByteArray(ItemsSketch.java:461)

Has anyone seen this before? Might it be related to memory corruption as we suspected in https://github.com/DataSketches/sketches-core/issues/175?