Hi,
You receive the assertion error because the request fails and you get bad credential error. So the XPATH set in assertion doesn't exist so you receive an error on assertion. The authentication fails in the request due to bad credentials.
Does the Database Cleanup(Deletes entries from database) testcase affect the DataSource Step(Excel data Source to get username and password)? in the other testcase.
It might be deleting the rows in the datasource or may be indirectly affecting? Do you have any scripts setup?
Let us know if this helps? Else log a ticket on the support form, attach the project(Right click on the project > Export project)
Thanks,
Jeshtha
