This could be similar to a bug that we fixed for release 5.18.0 (which will be released in a little over a week) where in some cases XML attributes were not being set on the correct element but actually 1 element above. If you have to know for sure that this is the same issue then I suggest filing a ticket so we can compare it between 5.16.1 and 5.18.0
Edit: after looking at the ticket I'm pretty sure your issue is resolved in 5.18, the Ccy attribute is being set on the right element. The test project still throws an exception but that could be due to different test setup reasons. Note this didn't go through the official support chain so you may want to let them know I already checked it out :)