possible annotative scale issue.

bad head definition, in this case Head4

Have AutoCAD select a group of pipe dimension blocks with a specific diameter or length. 

In this example I want to find and delete all diameters with a ?" as its value.

When trying to size a pipe, the units show up as millimetres/millimeters (mm) instead of inches OR the values for half show up as a backslash

When attempting to insert a pipe dimension you get the error "Invalid option keyword"

And the command prompt says "Enter an UNDO control option" with the dialog showing your choices

When attempting to insert a cap, it draws the pipe and dimensions it, but it doesn't insert a cap.

However if you draw a test pipe elsewhere, it successfully inserts the cap for you

A second copy of PIPEX blocks (SPRKDATA layer) appears on the drawing when using NWCOUT

When using Rapid Main or Rapid Line, clicking on the pipe causes a Fatal Error

When clicking the abacus to enter a length, you get this error;

Unhandled exception has occurred in a component in your application.  If you click Continue, the application will ignore this error and attempt to continue.

Index and length must refer to a location within the string.  Parameter name: length