Autocad seems "jumpy" and the screen occasionally flickers.  Sometimes, an in-progress command will cancel out when the screen jumps

 No inch marks (“) after the pipe diameter or there are but you prefer to remove them

Blocks with wipeouts are showing the wipeout rectangle 

When drawing objects, you get these icons/images/boxes next to the drawn object.  If you hover over it, it mentions an osnap option

Command is run, but nothing appears to happen. May get Nil message

All building dimensions are inserted into an different layer than the current one.

Dimensions are visible in paper space but not in model space.

When running the Line Couplings command (LC), you get the error, "No branch lines found crossing the line(s) you picked", even though it's 100% a fact the lines are intersecting

When running the Custom Coupling command [CC], the tooltip which follows the crosshairs duplicates the Command Line text, it does not show the drag distance and angle from the origin

The tooltip would be more useful if it showed the distance from the start point

Pipe Diameter does not get adjusted. New pipe not sized.