I've got a channel that conducts water to an obsidian factory. I did not control the water well, so there was too much water in the factory and in the lower part of the channel, after producing an obsidian batch. So I channeled a bit near the obsidian factory, so that the excess water flows away.
As soon as the water level in the channel got low enough, lthe dwarves started taking the channel. This channel must be a good shortcut to my magma smelters and forges.
Now, I have tons of dwarves and pets dead or bleeding to death in the lower part of the channel, where water is 2/7. I already noticed children and a few other dwarves with blistered feet, so I suspect some FB extract. I guess the water in the channel got somehow contaminated, and 2/7 is deep enough to soak the dwarves whith the deadly extract.
This is really a stupid bug.
My game was already spoiled by massive fill pond cancellation spam (another bug, which makes it difficult to detect other problems and understand what is happening in the fortress) and very low FPS (various animalsplosions, lots of HFS monsters in abandonned galleries, ...), but I was building an underground tower for a future king, and wanted to keep that fort until I have a king (never had one before). But now, these stupid deaths are quite demotivating... I don't even bother to close the channel to avoid more deaths.
This is not FUN, contrary to when I inadvertantly breached the adamantine vein and had to sacrifice lots of dwarves while walling the galleries, and then recover from the ensuing tantrum. Loosing because of mistakes is FUN, but not loosing because of stupid bugs.