[Web] - 500 Internal server error

When working in the web client, on creation or detach of an attachment appears error:
Error executing agent SwGetGlobalVariable
500 – internal server error
This behavior is pointing to the non-signed database. Please check is database signed with the server ID or the Id of the user that has enough rights to run unrestricted agents? If this is not the case, please sign the database and check this issue once again.
Please follow these steps to sign the database:
1. Copy database on to server (or on to local).
2. Open Lotus Domino Administrator, navigate to "Files" tab and select the database there.
3. Choose Files –> Sign...
4. Choose the following:
Active User’s ID to sign using with your ID.
5. Choose the following option to specify which elements to sign:
All design documents to sign every design element.
6. Select “Update existing signatures (faster)”
7. Click OK.