Steps to reproduce:
- Download the 5.0.3 war file from here and the HyperSQL file from here
- Extract the war file in its own folder
- Rename the xwiki-manager-web-5.0.3 folder to xwiki and move it inside your webapps folder of Tomcat
- Copy the hsqldb-2.2.9.jar file inside your xwiki/WEB-INF/lib folder
- Start Tomcat and install the UI with the DW
- After the installation is complete click on Continue
You should be taken to step 2 of the DW, but instead you're taken to your wiki's homepage.