D:\holly>witadmin importwitd /collection:http://hiserver:8080/tfs/hiproject /p:dev11 /f:dev11_task.xml
TF212018: Work item tracking schema validation error: TF26038: Field type for AppCompat.TestcasePassNumber does not match the existing type. It was String, but now is Integer.
Resolution:
1. Go to DB
2. Open table dbo.Fields
3. Find row TestcasePassNumber, and change the field Type and NewType value
4. It's ok and try a again.