On the forum there were some pictures of the laser focus cone. I think the laser will move lower with each pass, so the focus shouldn’t be a problem. But you only cut with the tip of your cone. That means the gap will only get a little wider than your tip. If you move deeper now, some of your cone will be cut off by the remaining walls. This will result in less power at the tip and might cause the inability to cut any deeper.
The image I remembered was of snapmaker original