It looks like on 1.4, specifying an interface as a source is broken:
trae@cr01b-vyos# commit
Using source address lo
Archiving config...
sftp://stor01z-rh8.int.trae32566.org:/int/cr01b-vyos Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/usr/lib/python3/dist-packages/vyos/remote.py", line 287, in upload
upload_sftp(local_path, url.hostname, url.path, username, password, port, source, progressbar)
File "/usr/lib/python3/dist-packages/vyos/remote.py", line 166, in upload_sftp
transfer_sftp('upload', *args, **kwargs)
File "/usr/lib/python3/dist-packages/vyos/remote.py", line 143, in transfer_sftp
sock.bind((source, 0))
socket.gaierror: [Errno -5] No address associated with hostname
trae@cr01b-vyos# show commit-archive
location sftp://USER:PASSWORD@stor01z-rh8.int.trae32566.org:/int/cr01b-vyos
source-address lo