If you notice that a vector is being cut more than once, try the following:

Select the vector(s)
Click Tools --> Object Manager
Click Arrange --> Break Apart
If you have duplicates, this breaking apart should generate visible copies in Object Manager
To clear out all the duplicates, try one of the following:


OPTION 1 - REDUCE NODES

Choose the Shape Tool (F10) which is under the Pick Tool.
You'll see different options across the top including an icon toward the rightthat has a tool tip that says "Select All Nodes".
Click that icon.
Then click the button next to it that says "Reduce Nodes".


OPTION 2 - MANUAL

Manually delete all but one of the lines
This is not a pretty option but sometimes the Reduce Nodes option just seems to do nothing.

You may also want to try Tools --> Simplify

If you are getting two cuts per line, you may not have duplicate data at all. If you zoom in, you may see that your data has resulted in a vector surrounding your original vector, meaning if you created a rectangle in your original application, you might now have a vector that goes all around the inside of that rectangle and then all around the outside of that rectangle. If that's the case, none of the tricks above will probably help you. I would suggest trying to save the data via another format and import that.

Note: a number of people have run into this problem and have found solutions but they don't seem to work consistently across different files exhibiting the same problem or across people. If you can improve on these, feel free to submit them and I'll post here.