I don't have permissions to open my files? There are several questions that seem similar, e.g., TextEdit shows dialogs about not having permission to open any files, but they're not exactly the same and none of the suggested fixes work.  Correction: when I posted, I forgot that one of the ideas in those posts I hadn't tried.  Because I was doing a long slow backup via rsync, I did not reboot.  This morning after that completed, a reboot has removed the problem.  But it would still be nice to understand why, and how to prevent—since it happened again today (see comments).

For more than a month, I've been using the "re-open windows on login" option to keep a few Textedit files easily accessible.  No problem noted with an occasional save or opening a new one.

But today, I cannot save any of them nor open any new ones in my home directory.  OS 10.12.1


There are no ACLs in the entire /Users tree.
There are no extended attributes on the file I am trying to open
There are no extended attributes on ~ nor on /Users
Windows I want to save have not yet been, so can't have extended
attributes
sudo chmod -R u+r,u+w /Users did not fix it
sudo rm -rf ~/Library/Autosave\ Information did not fix it
touch created the file, and vim can open, edit, and save it.
The school has a service which monitors the LAN for suspicious traffic.


There are some recent unusual events which don't seem capable of causing this, but just in case:


A post-graduate student's MacBook Air failed right before her
comprehensive exams.  She's blind, so learning Windows overnight was
not an option
I created a non-admin account for her on my MacBook Pro (MBP), help her set up VoiceOver, copied in her ~/Documents and a few other important items, and changed the UID (she was 502 on hers and 504 on mine)
Exams took three days (long difficult essay questions) during which she probably closed the lid to 'sleep' between tests rather than log out or shut down.
She logged out and handed me the MBP around ten hours ago.
I updated MalwareBytes and a scan found and removed OSX.Genieo (which AFAIK has to do with adware, not home permissions).  The previous version never found anything and I suspect wasn't even scanning (it took less than a half-second to say that it found nothing in over 500GB!)


Any ideas on a fix or a cause?
This post fixed my TextEdit permission problem:

https://www.cnet.com/news/fix-permissions-errors-for-sandboxed-applications-in-os-x/

I quit TextEdit, manually cd'd to ~/Library/Containers, and moved 
com.apple.TextEdit to my home directory out of the way, then restarted
TextEdit, and I was able to open files for which I was previously getting
permission errors.