Over the last few weeks, on several websites running older versions of Umbraco (< 7.2) we've have had issues with node creation in which child node permissions seem to disappear across the whole site.

When the issue is present, a user trying to create a document type in the back-end is given the standard 'There are no allowed document types available' message, but nodes have already been created under these items, and permissions were setup correctly. Sometimes a refresh will fix the issue but usually a site restart and application pool recycle is required.

This issue has been reported across different browsers, websites and networks. We are running no external libraries or plugins, and there doesn't seem to be any app logs to go along with it.

Has anybody else had a similar issue and found a solution? It seems strange that this has only begun happening recently.