Issue When restoring a snapshot an JsonApi error occurs

[Cannect]

Hi,

I am trying to restore a snapshot of a website in Web Presence Builder and get an error. Here are my server details:
OS‪ CentOS Linux 7.2.1511 (Core)‬
Product Plesk Onyx 17.5.3 Update #39


I get a popup with an error in my language.The error (translated) is:
Unable to connect to Web Presence Builder server. Please contact the server administrator.

When looking into the Chrome Network tab, I see two JsonApi requests:
https://www.myvps.com:8443/sitebuilder/JsonApi/ Status: 500
https://www.myvps.com:8443/sitebuilder/JsonApi/ Status: 200

And the output of both requests below:

Status Code 500:

1. {action: "SiteService", method: "restoreSiteSnapshot", data: [5, false], type: "rpc", tid: 22}
   1. action:"SiteService"
   2. data:[5, false]
      1. 0:5
      2. 1:false
   3. method:"restoreSiteSnapshot"
   4. tid:22
   5. type:"rpc"

Status Code 200:

1. {action: "SiteService", method: "log", data: [,…], type: "rpc", tid: 23}
   1. action:"SiteService"
   2. data:[,…]
      1. 0:"JavaScript error: Uncaught TypeError: Cannot read property 'success' of undefined on line 1 for https://www.myvps.com:8443/sitebuilder/js/minimized/Editor.js?1470121747"
      2. 1:"error"
   3. method:"log"
   4. tid:23
   5. type:"rpc"

I have tried to increase some PHP ini values in the PHP settings for this customer:
max_execution_time = 600
memory_limit = 192M
post_max_size = 2147483647
upload_max_size = 2147483647

But unfortunately that didn't solve my issue.