I'm merely suggesting an alternative to editing all of the pages based on the template.
the reality is that this is an issue that has plagued templates for quite some time, whether or not WebAssist extensions are used.
do a Google search on the error message, and you will find people experiencing the issue as far back as Dreamweaver Ultra Dev.
The only solution I have found for the the problem is the one to temporarily detach the page from the template.
If this does not work for you, then there is an alternative of using the Framework Builder to convert the template to a theme.
you can choose which solution to use.