While T269518 no longer blocks the process if another file has the same IA ID, the upload to Commons still fails if the filenames are similar enough to cause a warning during upload.

If you try to upload the file manually at Commons with a name that differs only in the extension, you get the following warning:

Which you can proceed past. I suppose ignorewarnings: 1 on the upload would fix this (not sure if you can ignore only a specific warning).

The warning in question is exists-normalized.