Hi, I'm new to the renovation scenario. I've recently completed my renovations, and found out that the flooring has even lines spreading across the floor. You can walk across it and it feels levelled just fine, but visually it looks like there are dips on the surface. When I asked my contractor about it, he tells me that it's because of the tiles below which causes this overlay issue.

I've attached an image.

Anybody ever experienced this issue before? Any advice you could share?

From the picture you posted it does seem that the tiles below are the ones that have gaps below them so as you walk they then become depressed