You could try to run the following powershell command :
$web = Get-SPWebApplication -Identity http://your web address
$web.ClientCallableSettings.AnonymousRestrictedTypes.Remove( [Microsoft.SharePoint.SPList],"GetItems")
$web.Update()
Source:
https://sharepointinaction.wordpress.com/tag/sharepoint-powershell-anonymousrestrictedtypes/
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