TYPO3 Core

Full TS-sample:

lib.aNewCe.renderImage = FILES
lib.aNewCe.renderImage {
references {
table = tt_content
uid.data = field:contentUid
fieldName = image
}
renderObj = COA
renderObj {
10 = IMAGE
10 {
file {
import.data = file:current:originalUid
}
altText.data = file:current:description
}
}
}

I can't reproduce this issue on master.

Test results:

altText.data = file:current:description

Displays the description of the file reference

altText.data = file:{file:current:originalUid}:description
altText.data.insertData = 1

Displays the description of the original file

The output seams to be correct