Dear Andy,

we have received your file. Thank you. It will take a while to fix this.
In the meantime you can do three things to avoid this bug.
1. prepare your image perfectly before loading it, that you do not have to change anything in the RIP.
2. Also play with the contrast if you change the brightness. The white will appear again at a point.
3. Do not use pure white. You can add 1 or 2 % black or yellow to the white.

Hope this will help you untill we have fixed the bug.