I'm having this problem with a 5.4 installation. I've checked the Name and the Task Name attributes and none have special chars. The Task Type is User, but I guess this has nothing to do with it... Any ideas?
Thanks in advance
In Designer you can generate the process and task forms via the built in form editor or generate them all using default templates (locate the generate forms button in the Designer top navbar). This warning says that Designer has looked at your Guvnor repo and was not able to find the forms.
Thanks, this solved my problem.