Thank you for pointing out this difference - we’ll mention it in the release notes.
The issue is caused by the fact that getItems() method now returns an unmodifiable collection instead of full copy as previously. So you now cannot modify the collection when iterating through it at the same time. But you can do the same as follows:
for (UUID id : orderLinesDs.getItemIds()) {
orderLinesDs.removeItem(orderLinesDs.getItem(id));
}
or
for (OrderLine orderLine : new ArrayList<>(orderLinesDs.getItems())) {
orderLinesDs.removeItem(orderLine);
}