Stream causes E_WARNING errors during Updraft backup

Hey guys,

We encountered an error caused by Stream while Updraft plugin is performing backup. You can see I also created a support thread for their plugin.

Can you shed some light on what can cause this error? See log below which comes from Updraft:

2092.365 (5) Resume backup (0a9f6db54c9b, 5): finish run
2092.393 (5) There were errors in the uploads, so the 'resume' event is remaining scheduled
2092.422 (5) PHP event: code E_WARNING: array_udiff_assoc() expects parameter 3 to be a valid callback, no array or string given (line 172, wp-content/plugins/stream/classes/class-connector.php)
2092.432 (5) PHP event: code E_WARNING: array_keys() expects parameter 1 to be array, null given (line 174, wp-content/plugins/stream/classes/class-connector.php)
2092.442 (5) PHP event: code E_WARNING: array_merge(): Argument #1 is not an array (line 181, wp-content/plugins/stream/classes/class-connector.php)
2092.453 (5) PHP event: code E_WARNING: array_filter() expects parameter 1 to be array, null given (line 192, wp-content/plugins/stream/classes/class-connector.php)
2092.463 (5) PHP event: code E_WARNING: array_unique() expects parameter 1 to be array, null given (line 194, wp-content/plugins/stream/classes/class-connector.php)
2092.474 (5) PHP event: code E_WARNING: array_values() expects parameter 1 to be array, null given (line 194, wp-content/plugins/stream/classes/class-connector.php)
2092.483 (5) PHP event: code E_WARNING: Invalid argument supplied for foreach() (line 638, wp-content/plugins/stream/connectors/class-connector-settings.php)
2092.499 (5) No email will/can be sent - the user has not configured an email address.
2092.508 (5) The backup has not finished; a resumption is scheduled

WP and all plugins are up-to-date. Thanks.

https://ww.wp.xz.cn/plugins/stream/