Can't clone WordPress site after migration

[Harm Jakob Tolsma]

I've used the Plesk Migration Manager to transfer a WordPress site from one Plesk server to another.
Since I need the copy to do some testing, I need to change the domain for the site.
Normally (when working on only one server) I just clone the site. However cloning the newly transfered site results in an error:

"Copying Files

• Task is not responding: id=1728, pid=30360, type=ext-wp-toolkit-backgroundtasksimplementation\cloning\cloningtask, currentStepProgress=-1, currentStepText=, initialTaskParameters=Array, isRestarted=1, referrer=/modules/wp-toolkit/index.php/index/list, runTaskUnderLogin=admin"

While I know that I can just copy the files and the database to the new site, I would expect the clone function to work.
What would be the way to find the problem and tackle the issue?

Source server is Plesk Onyx (Version 17.8.11 Update #53)
Target server is Plesk Obsidian (Version 18.0.26 )
Not sure if this is relevant, but perhaps worth noting.

 

[IgorG]

Please check that is your case Unable to clone WordPress: Copying Files Task is not responding

 

[Harm Jakob Tolsma]

Please check that is your case Unable to clone WordPress: Copying Files Task is not responding

I don't have an LVE Manager. Server runs on Ubuntu 16.04.6 LTS

plesk db "select startTime,id,type,status,finishTime from longtasks where type LIKE 'ext-wp-toolkit%' order by startTime desc"
+---------------------+------+------------------------------------------------------------------+--------+---------------------+
| startTime           | id   | type                                                             | status | finishTime          |
+---------------------+------+------------------------------------------------------------------+--------+---------------------+
| 2020-04-17 08:20:18 | 1729 | ext-wp-toolkit-backgroundtasksimplementation\cloning\cloningtask | error  | 2020-04-17 08:20:20 |
+---------------------+------+------------------------------------------------------------------+--------+---------------------+

 

[IgorG]

Most probably the issue related to Plesk bug PPPM-11017:

[BUG] Unable to clone WordPress: "Copying database" fails without errors

Applicable to: Plesk for Linux Symptoms Unable to Clone Wordpress site: Domains > example.com > Clone Wordpress site, it fails on "Copying database" action without actual error: P...

support.plesk.com

 

[Harm Jakob Tolsma]

Panel.log shows

[2020-04-17 07:54:47.755] ERR [extension/wp-toolkit] mysqlcheck: Got error: 1045: Access denied for user '[USER]'@'localhost' (using password: YES) when trying to connect

[2020-04-17 07:54:47.764] ERR [extension/wp-toolkit] Warning: mysqlcheck utility has detected some issues with the database of the source WordPress installation. You can find the details below. Continue the cloning if you think these issues will not affect the cloning procedure. Error message: mysqlcheck: Got error: 1045: Access denied for user '[USER]'@'localhost' (using password: YES) when trying to connect
...
[2020-04-17 08:20:19.681] ERR [panel] ERROR: escapeshellarg(): Input string contains NULL bytes (functions.php:1150)
[2020-04-17 08:20:20.783] ERR [panel] Task is not responding: id=1729, pid=447, type=ext-wp-toolkit-backgroundtasksimplementation\cloning\cloningtask
[2020-04-17 08:20:20.783] ERR [panel] Task is not responding: id=1729, pid=447, type=ext-wp-toolkit-backgroundtasksimplementation\cloning\cloningtask, currentStepProgress=-1, currentStepText=, initialTaskParameters=Array, isRestarted=1, referrer=/modules/wp-toolkit/index.php/index/list, runTaskUnderLogin=admin