We too had noticed the same problem. However things seems to be ok when done using the API. The human task view (Eclipse Component) seems to be screwing up something. Was found out by a colleague. Was too tired to debug more.
However, if you check the commands received on the server you might be able to understand why this strange behaviour is there.
Also we notice that it doesnt occur when using H2 database, but strangely appears when using MySQL database.
Regards,
Franklin