If you set a wall to be bombable (on the north wall, maybe the others; haven't tried), then link cannot move up through it once he bombs it. He'll get stuck.
If your tileset is normal, you can't see what's going on, as the wall is likely set to overhead. However, using the Freeform dungeon rule and special non-overhead wall tiles to see what was happening, it turns out that when he walks up to move to the next screen, and he gets to the very top (y:-16), he jumps back to x:0. If you continue to hold up, he continues to do this, walking up and jumping back.
If you try to press down once this starts, he can't move (probably because he's now stuck in a wall which would normally be taken care of by the dungeon-door code).
I experienced this in alpha 233, but I do recall that bombable walls work in older versions.
Confirmed - I just made a new quest (in 254 win), and Link just stands in the bombable hole - the screen doesn't scroll.
Just a possibility:
Are there solid combos in the next screen?
Is "smart screen scrolling" on?
In my own case, both sides of the wall are set to bombable, so either:
1. that feature (linked bombable walls) is working, and this is something more sinister, or,
2. ZC isn't bombing the other side of the wall.
I don't recall, but I believe it DID bomb the other side of the wall when I used the walk-through-walls cheat to get to the other side, so... I'm betting on #1.
Edit: Oh, and, as I'm not even sure what Smart Screen Scrolling does (and have been too lazy to check), it's not enabled.
smart screen scrolling is kind of broken, but it's basic purpose it to prevent link from walking into solid combos on the next screen and therefore getting stuck.
My understanding was that this did not work with walk thru walls and I think bombable ones too.
Turns out that I DO have Smart Screen Scrolling checked, although I'm not sure how or why. I'd rather have it than not, however.
Either way, as a curiosity, I create a brand new quest, changed the first DMap to dungeon, stuck link in 0x10, and set the north wall to bombable. I also dropped left a bomb pickup for link. I then went up to 0x00, set the south wall to bombable, and saved.
Upon testing it, Link is able to bomb the wall, but not walk through it. It still treats the upper row of wall as solid.
So, I went back into Zquest, and modified the combo so that it was walkable. I tried again, and was able to walk through to the next screen. However, I then found myself stuck in the opposite wall, as it wasn't bombed.
I then realized the level number was still 0, so I bumped it up to 1. Then, everything worked fine.
So, now, I'm making the following assumptions:
1. My problem was caused by Smart Screen Scrolling
2. Dungeon DMaps on level 0 don't do doors properly (a known issue/feature)
I know there's a bug in there somewhere, but I'm not entirely sure where or what...
If it works once you changed the level number then this shouldn't be a bug anymore. Level 0 is reserved for overworld dmaps so things like bombable walls really wouldn't be used then. I believe this is a feature.