ModSecurity works well to stop common exploits, but there are times when ModSecurity can work a little too well and block legitimate requests in scripts as well.
So if you are experiencing ModSecurity blocking your scripts frequently with 403 errors, then a solution may be to disable ModSecurity completely on your account.
While we do not recommend disabling ModSecurity, you can submit a request to our Support department requesting that ModSecurity be disabled for your account.
Please note: Disabling ModSecurity increases your accounts vulnerability to exploits and malicious activity and is not recommended.
Disabling ModSecurity in cPanel.
Go to: Security --> ModSecurity
From there you can disable it on a specific domain or your entire account.
Again, please keep in mind that ModSecurity can protect your account from known exploits and common hacks, so it's not recommended to disable it unless you know what you are doing.