When creating linework in your main drawing, you're noticing that some or all of the linework in one or more of your Xrefs is becoming excessively thick.
You might be having this issue when drawing lines for lateral or mainline irrigation pipe.
The system is turning on display line thickness, and the Xref has it set to improper line thickness.
1. Type LAYER in the Command line and press Enter.
2. In the Layer Properties Manager, expand the Xref layers.
Set the lineweight to Default for each Xref layer.