1.
I'll start with toilets since I'm reasonably sure you know about this, what with them not being fully implemented.
Here's an album cataloging the problem. http://imgur.com/a/ghul2

It occured after a save/load cycle so that might have something to do with it. Basically the toilet could not be cancelled like other objects, and seemed to behave as a plant. Chortle. When built, it still had the green outline, and forced the colonists into an endless loop of attempting to build an object that was already there.
2.
The second, perhaps more critical, problem is that save/load cycles that don't include restarting the game cause colonists and the IMP to ignore every object built or ordered before the save was made. After the load, they all stood around doing nothing at all, not repairing anything, not building anything, and I even got an email asking me for a workshop table despite there being two that had previously been used without issue. When I ordered a new table, they went around building that and any objects ordered afterwards. The IMP ignored previously given dig commands until I cancelled and re-gave them. Critically, they would not interact with anything that hadn't been placed after the save.