Cannot Add or Edit Components in Touch UI

Seeing this issue across both development and stage on our AEM 6.5.12.0 instances, while working in Touch UI over this last week: "The issue is that periodically ALL components will have their edit options removed, just leaving the Insert and Group options." (Same issues as this thread and this thread, which had no resolutions)

Suddenly seeing only Copy, Group, and Convert to EFV:

Additionally, the add component button on any parsys has disappeared:

The above screenshots are from our stage environment on an administrator account. The same issue is present across other user logins. There are no obvious errors in the granite logs or the web browser console.

Fixes attempted without any results:

• Reinstallation of UI (apps) packages seemed to temporarily restore some functionality sometimes? But then it would occur again very quickly.
• Suggested Band-Aid fix from this thread to specify "cq:actions" in the cq:editConfig node across components has been unsuccessful in this case.
• Reverted any recent changes to a git history period prior to when the issue began.
• Traced back permissions being served to the render function for the menu options, and found the same issue as this post: "For the line starting return ns.pageInfoHelper.canModify(), I think there is some data missing in the page info json object. On my broken machine, I cannot see a permissions array."

Any insight/suggestions are appreciated.