Strange ends on my pencil lines

My question is about Illustrator. I like to use a pencil at 0% Fidelity (Accurate), 0.25 pt stroke/no fill to draw lines that look hand drawn. I then expand the lines. But I keep getting some proportion of lines that don't have a butt end, and instead have a sharp pointed end or a blob of anchor points. I need clean butt ends on my lines, so I then try to use the eraser on the messy ends of my expanded lines. Sometimes this leads to nice butt ends, but other times the line I drew gets completely changed and changes from a line to a sharp pointed shard. I did a test where I drew a series of lines with the characteristics listed above and used the Stroke Panel to change the end types (Butt, Round, Projecting) and the corner types (Mitre, Round, Bevel). No matter what Stroke attributes I chose, most of my lines had butt ends, but a small percentage had sharp pointed ends or blobby ends. Can you please help? Thank you