I was able to locate the problem and fix it.
Another problems are three repeating regions on the detail page.
rspricetable will return rows, but only if at least 10 rows can be returned (depending on the product). For less rows it returns nothing.
rsextraimages returns nothing.
rsversions returns all rows online, but not on my local server
I have tried deleting the behaviors and adding them again, but it made no difference. I also tried setting to the behavior to an arbitrary number for rows to be returned without any change.