The problem occurs when the printer is set wrong, therefore the label is bend.
The weight of the label roll ensures that the feeder is not pulling the label uneven. But as the roll is used up and the weight decreases the feeder pulls the label unevenly and the bending begins.
1. Make sure the skrew is no thighten too hard. This will counteract the feeder.
2. Make sure the feeder is not pressing upon the label from both sides.