We've faced an issue duplicated entries in tig_ma_jids table which caused some strange behaviour. After analysis, it turned that the DDL SQL in MySQL version doesn't create unique constraint on jid column:

private static final String MYSQL_CREATE_JIDS =													"create table " + JIDS_TABLE + " ( " + JIDS_ID															+ " bigint unsigned NOT NULL auto_increment, " + JIDS_JID															+ " varchar(2049), primary key (" + JIDS_ID + ")); ";

For other database types looks like you add "JIDS_JID as unique.

Here is message archiving plugin version info (extract from MANIFEST.MF):

Implementation-Version: 1.2.0-b122/dded3368

Bnd-LastModified: 1485790200209

Bundle-Version: 1.2.0

Implementation-Build: 122/dded3368 (2017-01-30/15:29:53)