Hi! What you are describing is usually called “lippage,” and it is honestly such a trip hazard. I had this problem in my hallway, and it drove me crazy every time I stubbed my toe. Most of the time, it happens because the installer didn’t level the floor properly or used large tiles without the right clips. I wanted my living room to look perfect, so I contacted Dream House Tile https://dreamhousetile.ca/ to redo the main floor area. They specialize in large-format slabs and porcelain, so they know exactly how to get a perfectly flat finish. They offer some of the best tile installation services in Toronto and GTA, and you can see their portfolio online. Their team has over fifteen years of experience, so they can tell you if it’s a structural issue or just a bad install.