Fixed. It was a bug in CPG 1.6.15, only allowing 512 characters in description. Of course there is an admin setting for that and we set it to 99999, but somehow it defaulted to 512, the setting was ignored.
Thanks to @Callimachus for that detailed description of the problem, because most of the time identifying it, takes most of the time.
Hopefully the CPG team will fix that in future versions.