Iron_Cedar Based on what I see in your pics, I think the error message is not giving the correct error statement. It happens when the game can't find a message that is right for the situation and defaults to something else. What I see in the pics is that you are placing an object (upright piano?) off grid next to a bar, also off grid, and the former is overlapping the latter's footprint so you get the error without MOO being on. I'm not sure though as I can't see enough of the build to be absolutely sure. So, if you would like, I am willing to take a look at the build to see if I can find anything more that could be causing the issue. All you need to do is upload the lot to the Gallery and reply here with the name of the lot and your user ID if other than the one you use here (Iron_Cedar).
Hope this helps.