Edit History

Hello, i'm looking for help in trying to fix my prestashop website.

A couple of days ago the website randomly started returning an error page saying 

Insufficient Storage

The method could not be performed on the resource because the server is unable to store the representation needed to successfully complete the request. There is insufficient free space left in your storage allocation.

Additionally, a 507 Insufficient Storage error was encountered while trying to use an ErrorDocument to handle the request.

Not every time, just a couple of times and then it went back to normal.

I have plenty of storage on my shared hosting so that is not the issue. A quick googling told me that it was caused by hitting cpu or db resource limits so i went to cpanel resource usage page and there was a spike in cpu usage, number of processes and faults (i'll attach some screenshots).
As you can see it's not high all the time, it stays high and occasionally fault for some hours, then goes down with no fault for some time and then back up. Could this be bots accessing the website?
Before this started, nothing was changed other than usual products uploading and modifications. No modules were installed or modified.
After it started i tried to "fix it" by updating to the latest non major version (from 1.7.8.5 to 1.7.8.11 i think), and update the theme. Did not help, not for long at least. I then tried to clean the db by deleting old abandoned carts and logs. Back office sped up but still did not help and i occasionally got the error page while visiting the website (either front or back office). I think that while i put the website into maintenance mode to do some work the usage dropped, so this might be a clue.
As you can see from the screenshots, on a normal day the usage is steady low, few processes running. When this issue started usage goes gradually up until it starts having like 20 processes, hitting limits and then faulting.
I could try to disable modules, but i would have to do it while out of maintenance and clients would load a broken page, so i'm hoping there is a better way that helps me understand what actually are those processes, what is spawning them and if they are caused by a fault module or something.
I have access to cpanel, db and ssh.