Can't modify page on Connect IQ store

Modifying Connect IQ store watch face category responses with the next error message: 

„We found one or more errors on the submission form.“

without any explanation what is wrong. 

The only modification that triggers the error is changing a category of the watch face: https://apps.garmin.com/en-US/apps/3532114a-c93c-447a-bc8e-25999ea599fc