Ok, just migrated my main sites to CP.
Just one had a little trouble.
The migration plugin don’t seem to check if it can overwrite files.
The plugin, during migration process, stopped with an error (something like) “can’t overwrite XXXXX”. Reloading the page a nice white screen. No problem for me, I’ve manually migrated from command line in one minute.
It could be useful to check file permissions before starting the process.
Do you recall which files weren’t able to be overwritten?
I have seen the issue with the composer.json but the update still completes.
No, sorry! I just recall that was a php file.
Ok… funny breaking friends’ site to test 
Warning: copy(/var/www/vhosts/redacted/httpdocs/wp-includes/class-wp-feed-cache.php): failed to open stream: Permission denied in /var/www/vhosts/redacted/httpdocs/wp-admin/includes/class-wp-filesystem-direct.php on line 247
Warning: copy(/var/www/vhosts/redacted/httpdocs/wp-includes/class-wp-feed-cache.php): failed to open stream: Permission denied in /var/www/vhosts/redacted/httpdocs/wp-admin/includes/class-wp-filesystem-direct.php on line 247
Disattivazione modalità di manutenzione in corso…
Impossibile copiare il file.: wp-includes/class-wp-feed-cache.php
L'installazione non è andata a buon fine