But how did it happen that one part of it allows me to follow it, and the rest, on the contrary, works as it should? Judging by how you described it, the texture of the crack in the program remembered that it should be "beneath", which allowed the player to walk on the wall, but what about the table?
Viewing post in Cruel Serenade Discussion (The first game)
Like I said, that's just one example of what can go wrong. Another: tiles can also have directional collision. Say you have a tile with a fence on the far right side. You still want to be able to exit and enter it from the top, bottom and left, just not the right. So you can set that. This can cause problems if you set this up custom for a tile and then forget about it. You can also set certain tiles to programmed "regions" and, with a plugin, tie specific lighting effects to those regions. If you want to just apply the lighting effect without a new tile being visible, you can use a fully transparent tile...but then it's easy to forget you've placed that tile, and you can have the crack situation all over again. The tiles for the tops of walls are tricky, because they're usually impassible/"same as character", but what if you want to be able to climb a ladder and then walk around on those tiles, but still collide with them when you're on the ground? And on and on.
I actually have no idea what caused this particular collision issue, and it's not worth the time to fully figure out. Luckily I don't have to: RPGMaker MV has a brute-force "fix it" solution for this that works every time: you just put down an empty "event" on the tile. Events are programmable containers that are used for npcs, buttons, anything that changes throughout the game basically. And they ALSO have a "layer height". But THEIR layer height always overrides anything else on the tile space. So I just put down an invisible (to the player) event, set height to "same as character", and no more walking on the table. Ideally of course I WOULD figure out the actual problem and fix it, because slapping these down everywhere introduces clutter. But sometimes it's difficult or impossible to say why the issue is happening, and sometimes it's obvious WHY, but there's no easy solution, so I have to resort to this.
To answer your question directly: Something is different on those counter tiles at the bottom that's causing this. What is it? No idea. But I can still fix it, so I have.