This document applies to Avid Studio and Studio 16.
This is most likely normal. If you added content to the Timeline by clicking on the Send or drag clip to the timeline button, it is possible that the clip may go to a timeline track that you were not anticipating. If you add a clip to the timeline in this manner it will always go to whichever track is currently designated as the Primary Track. You will know if a track is designated as the Primary Track by the presence of an orange highlight on the left edge of the track. This track is also a slightly lighter shade of grey.
If you meant to add the clip to a different track, simply drag the clip to the desired timeline track. If you intend to add more clips to the timeline in this manner, please ensure that your Primary Track is set appropriately.