Posted this to PZC's B10 thread, but it was requested here as well, so here's a relatively obscure but also severe problem I discovered.

Angled Walk Corner Crash: [Demo Quest]

This is directly related to 8-way movement.

If you exit the bottom left corner of an open screen by walking diagonally downward-left, and you walk into the precise corner of the screen - like, the exact corner pixel - ZC can't seem to make up its mind whether to scroll sideways or downward, and simply decides to crash instead of scroll at all.

This only affects downward-left screen exits - downward-right, upward-left and upward-right all work fine.

DMap type is irrelevant - it happens on Overworld, NES Dungeon, Interior and BS Overworld types. Link's hitbox size is irrelevant. Combo type is probably irrelevant - I tried it with standard ground (none), slow walk and shallow water, all to the same effect.

It requires a bit of precision to duplicate, but fortunately, it was easy to set up for recreating in the room that truly matters.

In the demo, you start in the room with the corner crash (marked by the red x). Walk left into the gray angled barrier, press down while still holding left, and that diagonal walk should crash you when you hit the bottom left corner of the screen. (It would probably be good to load the quest, exit ZC, then start the program again so that you don't have to keep reloading the quest after the crash.) The other rooms have adjusted angled barriers for testing, but you won't need to use those, so just ignore them (they each take some F4 frame-advance movement to position Link perfectly anyway).

Here are the 2.5x program versions I tested this on, including package name and date, and which ones crashed:

ZC 2.50.0 (official): All good.
ZC 2.50.2 (official): All good.
ZC 2.50.3 RC1 ( | Dec. 04, 2016): All good.
ZC 2.50.3 RC2 ( | Dec. 04, 2016): All good.
ZC 2.53.0 B1 ( | Jul. 10, 2017): Crash introduced.
ZC 2.53.0 B2 ( | Jul. 14, 2017): Crash.
ZC 2.53.0 B4 ( | Aug. 17, 2017): Crash.
ZC 2.53.0 B10 ( | Oct. 02, 2017): Crash.
ZC 2.54 B52 ( | Jan. 20, 2017): All good.
ZC 2.55 A ( | Durrr): Crash.

I didn't think it was worth checking every beta between 4 and 10, but I could, if it's absolutely necessary.

For the record: the behavior before the crash was for the screen to scroll downward.