Cloud sync to Wasabi fails with "Can't mix absolute and relative paths"

Set up a Cloud Sync task in FreeNAS to sync to Wasabi, I get an instant failure.

The settings are very straightforward:

Direction: PUSH

Remote folder: /

Local folder: /mnt/tank/folder

Transfer Mode: SYNC

No Snapshot

Exclusions:

/caches/**

I'm using the exact same settings to perform Cloud Sync to Backblaze B2 and that doesn't fail with the "Can't mix absolute and relative paths" error.

Error: Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/middlewared/job.py", line 349, in run
    await self.future
  File "/usr/local/lib/python3.7/site-packages/middlewared/job.py", line 386, in __run_body
    rv = await self.method(*([self] + args))
  File "/usr/local/lib/python3.7/site-packages/middlewared/schema.py", line 961, in nf
    return await f(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/middlewared/plugins/cloud_sync.py", line 1002, in sync
    async with self.local_fs_lock_manager.lock(local_path, local_direction):
  File "/usr/local/lib/python3.7/site-packages/middlewared/plugins/cloud_sync.py", line 473, in lock
    if os.path.commonpath([k, path]) in [k, path]:
  File "/usr/local/lib/python3.7/posixpath.py", line 514, in commonpath
    raise ValueError("Can't mix absolute and relative paths") from None
ValueError: Can't mix absolute and relative paths