Please try this for recreate the bug:
1., Add "ProSites" status for one blog
2., Remove the "ProSites" status from the blog
3., Try open the blog or Dashboard of this blog
When you'll try open these pages, you will get similar error line in error.log file:
[Thu Feb 16 06:24:55.785890 2017] [:error] [pid 19400] [client 184.108.40.206:54433] FastCGI: server "/var/www/clients/client0/web1/cgi-bin/php5-fcgi-144.276.209.55-80-site.com" stderr: PHP message: PHP Fatal error: Call to undefined method ProSites::get_profile_id() in /var/www/clients/client0/web1/web/wp-content/plugins/pro-sites/pro-sites-files/gateways/gateway-paypal-express-pro.php on line 3146
There isn't requied to set custom domain for repeat this bug, just add and revoke "ProSites" status.
Secondary question: Is there any option in Settings page what can do this error?