This is a bug in the 1.8.5 distribution, thank you for detecting it. There are two versions of the BatchChannelExtraction script, one of them obsolete. While I release an update to fix this issue, make sure you execute the version where the .js file is stored on a "src/scripts/BatchChannelExtraction/BatchChannelExtraction.js" dedicated subdirectory. This should be the first item available from "SCRIPT > Batch Processing" on the main menu.
Thank you for reporting this problem, and sorry for the inconvenience.