If you come across File Transfer Failed Error 451 on Filezilla, there is a possibility the server is maxed out. This may be due to httpd error logs maxing out the hard drive and/or from a broken or corrupt database from your WordPress install.
Fix Running VestaCP with Centos 7 and WordPress installs
Check httpd logs in SSH to see which folder is way oversize. If it’s the “domains” folder you can delete this folder and all of its contents to clear the space again
cd /var/log/httpd/ du rm -r domains mkdir domains service httpd restart service nginx restart service vesta restart
This should get things working again, but keep a close eye on the CPU processes while your working with your site. If the problem persists this is just a bandaid and you will have to do some more digging into the httpd processes to troubleshoot. Good luck!