Not certain this will fix it, but it seems like an issue with the config files. Try deleting the P3P xml from the config folder and restart the program. If it keeps happening you may have to manually edit it with notepad to set Compression and Use Extracted Files to True Yup, deleting the file work...

Trying to install the Pesona 3 Sappho Edition and Free Camera mod but when building mods I'm met with this error message.

"Unhandled Exception occurred while building:
String was not recognized as a valid Boolean."