The info.magnolia.dam.app.ui.field.definition.DamUploadFieldDefinition is not i18n enabled
https://documentation.magnolia-cms.com/display/DOCS/DAM+upload+field
This is reproducable on our demoauthor instance.
If I insert the value "true" for i18n parameter (i18n: true) the binary information (binaryData, extension, filename…) is always saved on same node (binaryNodeName: import). In oldest version (Magnolia 5.3.x) the information was saved on a different node: binaryNodeName + language; ex. import_en
form:
tabs:
name: tabUpload
label: Upload
fields:
name: upload
class: info.magnolia.dam.app.ui.field.definition.DamUploadFieldDefinition
label: Upload asset
binaryNodeName: import
i18n: true
editFileName: true