its somehow hard to describe, so i made a video:
https://www.youtube.com/watch?v=XUj1OWs2TrI
i try to describe it anyways. when you put multiple vertical redstone ladders made out of glowstone right next to each other, the redstone in the whole thing will not update properly after one point has been powered.
i tested it in 1.4.2pre since the video is from 12w42b, its still not working properly.
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Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
yes, in 1.4.5 prerelease the bug is still there
Fixed as of 13w01a.
That has nothing to do with glowstone/slabs going upwards, also glitches in the floor.