Duplicate batch insert stmts are being generated when identity key generator is in use on a table.
I've included an IntelliJ14.1 sbt scala project which demonstrates this in its log output.
e.g. 5 jdbc insrts are turned into 10 by duplicating each stmt sent to JDBC.
Search for the BatcingBatch debug text in the log to confirm the batch size.
H2 trace level also confirms it.
By switching to manual key gen the problem can be avoided.

Cheers,
Lee