Hi Kyle, Hi All,
found the solution that I am reporting as it may be useful for others.
To solve the issue, I needed to edit the plan and delete the description. Then save. Then open and add the new string.
For some reasons, if I just delete the old description and write the new (in my case the language string) without first saving, the system was presumibly keeping some dirty character or similar. Something like using a joomla editor that I was NOT in fact using.
Hope this helps!
Thank you
Cristiano