SOLVED After upgrading the plugins to the latest releases, the project still failed to be built with the same error. It was actually a mistake in the root pom.xml.
Turns out the root was the presence of a "< scm >" tag in one of the pom.xml files.
Removing the following tag allowed the maven release:perform task to be run:
REMOVED:
<scm>
<tag>itabuy-common-root-2.06</tag>
</scm>
Thank you khmarbaise and Robert Scholte for your help.