u/Groundbreaking-Ad481

Hi! I'm an InDesign beginner, and I don't know what's the deal with these weird white lines. and I asked my design teacher for help with and she said those wouldn't be visible when printed and that it was just the PDF preview, so I did a test print and they're still there. I thought it was a Photoshop cropping issue, but it's not, and when I zoom in, the lines disappear. Any help would be greatly appreciated!