When more than to upload fields are defined in a Content app or in a dialog, when the dialog is saved just one of the uploaded files is saved. Upload fields save many properties, this properties are saved in JCR as separately properties instead as node with this properties. To do it the docu was follow: https://documentation.magnolia-cms.com/display/DOCS62/Upload+field

Steps to reproduce
1. Create a content app with two upload fields (see attached example).
2. Open the app and create a new item uploading two diferent files.
3. Save the new item.
4. Open the item to edit it. Both upload fields are displaying the same file.

Expected results
Both uploaded files are stored separately and when opening the item to edit, both uploaded files are displayed.

Actual results
Only one of the uploaded files are stored in JCR, the last one.

Workaround
Not using two or more upload fields in the same dialog.
Using info provided in MGNLUI-5656 it is working (maybe it was not documented??):

upload:
 class: info.magnolia.ui.editor.UploadViewDefinition
 required: true
 itemProvider:
 $type: jcrChildNodeProvider
 nodeName: image1

Development notes
In JCR everything is stored at item level, the upload field name is not taken into account. It means that when storing the second uploaded file, the first values are overriden.

damUploadField is also affected.