Cannot drag & drop element to Form elements in content

Found in

EPiServer.Forms 4.11.0

Fixed in

EPiServer.Forms 4.14.0

(Or a related package)

Created

May 10, 2018

Updated

Jun 12, 2018

State

Closed, Fixed and tested

Description

Step to reproduce.

1. Login to a CMS system that has installed Forms.
2. Create new a Form.
3. Click to publish that Form.
4. In All Properties mode, drag & drop the first element to Form elements.
5. Drag & drop the second element to Form elements.

Expected:
You can successfully drag & drop two elements to Form elements.

Actual:
At the second drag & drop, the system shows this message:
*"Could not save property, and it has been reverted. Please try again.
ContentReference: Input string was not in a correct format."*