I have upgraded the site from 9.3.1 to 9.8.3 and installed the EPiServer Forms 18.104.22.168. I have drag and drop Selection and Multiple or Single choice Form elements and when I try to add items i am getting this error "Unable to load /EPiServer/cms/Stores/contentdata/ status: 500"
Hi, this is a bug CMS-3486 with Forms 2.1 and CMS 9.8.3. I am sorry for this.
For work around, please install specific version of CMS 9.8.2.