I built a channel from the outside river, ran it indoors, and connected it to a floodgate & lever to irrigate a mini-farm for my first growing season.
Attempted to disassemble the lever & floodgate during the first winter, once I had my real farm built further inside the mountain.
The lever disassembled just fine, but my dwarves have been unable to remove the mechanism from the floodgate. They keep walking over to it, pausing for a few moments, then flashing a question-mark above their heads and walking away. Then a few seconds later, another dwarf will start over to try the same thing.
Examining it with 'k' shows that the floodgate and mechanism are still linked together, in the same square. The graphic on the screen is the one for mechanism, not the one for floodgate.
The trade screen - which lists every object in my fortress - shows that floodgate with a red "inaccessible" tag.
I tried digging out the walls all around it to provide better access, but that didn't help. Then I thought perhaps the problem was proximity to the channel itself, so I engineered a cave collapse which knocked it away from the channel. Still didn't help.
Is there any way to remove this floodgate/mechanism, or are my dwarves doomed to struggle with it for eternity?