Summary:

When creating a new task under a company the wave activity field is holding its context from the last task created.

Symptoms:

When creating a new task a user selects the option to "Show Campaigns" and a user then links a wave activity to this task.
When a user goes to create a new task, the wave activity field is already filled in with the information form the last task created and when a user saves the task, the task is linked to a campaign. 

Resolution / Workaround:

A workaround would be to manully clear the wave activity field when creating a new task.

Status:

This issue has been resolved in Sage CRM 7.3d.