Browsing Account items inside a backup in WHM fails with:
An error has occured. Please try again later or contact your administrator.
In plugin error_log, you see this error:
2018-11-16 22:18:36 5beea78c01b3b ERROR Cannot obtain list of accounts. File: /usr/local/cpanel/base/3rdparty/acronisbackup/Application.php Line: 86
The issue has been fixed since build 253 of Acronis Backup plugin for WHM & cPanel. Please update to the latest build.