If you have imported artwork as a vector file, that artwork is flagged by the program as ‘newly imported art’. With this art, the program assumes the sequence is not designed to sew.
As you assign stitches to objects, the program will begin sequencing the objects to the end of the design. The purpose of this is to allow you to perform both jobs simultaneously; assigning stitches and creating the sequence that the objects will be sewn.
If you do not want this to happen on the imported file’s objects, simply select it in its entirety and click ‘Line’. This has the effect of clearing the ‘newly imported’ state.