Customer found his own issue:
I had a look at the source code for the java driver and found the error there. It is in:
Right after calculating the number of "remaining" keys, it sets the limit of the query to the remaining number of keys and re-runs the query. What is missing here is:
To actually start from the entry after the last entry on the current page. I have tried this and it works. But there is more code in this method and it is not very easy to follow so important to make sure that this fits.
I am enclosing a diff.