Of course, that stray purple wall isn't supposed to be there. The graphics don't actually have any effect: you can enter the squares that are erroneously drawn as wall just fine (as long as the real tile isn't also a wall), and if any tile is forced to go through an animation while it's being masked by one of these stray graphics, it reveals its true self when it starts the animation. For instance, this was the case where the row of fake wall meets the column of light blocks: it was originally drawn as part of the purple wall, until the snake pushing the block line caused them all to go through the shudder animation.
That screenshot shows version 3.3.1.0 because that's what I've applied my patches to (such as the expanded timer). For completeness, I also tried loading the level on a freshly-extracted 3.3.1.2 that had no change from vanilla (not even a recompile), and got the same result.
Level 30 itself has never changed in all of this: it's still the same untouched file, size 114173, md5sum a7369298fcac6db2547ef04f41c34072. It looked just fine when I recorded this video, so what could have caused it to start acting all wacky?
that main problem is the damaged cache.
), but very much hampered by the fact that at many levels "amoeba" growth rate absolutely abnormally (too fast), because of that almost instantly floods the level