in nstest: XSLA6: Cannot recover from database & and 40XT4 errors in nstest (sane jars) after ASSERT FAILED org.apache.derby.shared.common.sanity.AssertFailure: ASSERT FAILED inconsistency in space management during insert

With the 10.8 (10.8.2.2) tree sync-ed up to revision: 1179754, I ran NsTest Embedded with sane jars, but no derby.properties file.

I saw the following AssertFailure:

org.apache.derby.shared.common.sanity.AssertFailure: ASSERT FAILED inconsistency in space management during insert: slot = 146 getSlotOffset(slot) = 3206 dataWritten = 19 freeSpace = -15 firstFreeByte = 3149 page = ---------------------------------------------------
page id: Page(378,Container(0, 1153)) Overflow: false PageVersion: 895 SlotsInUse: 159 DeletedRowCount: 93 PageStatus: 1 NextId: 317 firstFreeByte: 3149 freeSpace: -15 totalSpace: 4028 spareSpace: 0% minimumRecordSize : 1 PageSize: 4096

This was followed by:

------------ BEGIN SHUTDOWN ERROR STACK -------------

ERROR XSLA6: Cannot recover the database.

and somewhat later:
ERROR 40XT4: An attempt was made to close a transaction that was still active. The transaction has been aborted.

But after a while we get back to the errors always seen with this test (ERROR 22003 and XBM06).

I will attach the derby.log, in case someone likes to look at puzzling behavior.