According to SAP, this is the fix for our case: "SAP Note 2233772 - Axis XI30DynamicConfigurationHandler does not handle composite values correctly".
Just as a reminder, in our case everything was working for more than one year without any recent channel adjusment, so it wasn't because of any channel configuration change.
As I mentioned before, we recently applied the SP16 to our PI 7.31 Java SP08, and one of the notes contained in that SP (2174163) had a side effect, fixed by the recent 2233772 above.
Regards,
Douglas