Intermittent Access Denied errors for anonymous users I'm running into seemingly random Access Denied errors that occasionally come up on most (but not always all) node pages for anonymous and low-level users (anyone without the "Bypass content access control" permission).


I've rebuilt permissions a few times, which fixes it for awhile too, but the behavior returns.
I've scoured user permissions and don't think there's anything incorrect in there. 
We are not using any contrib node access modules.


Clearing the site caches fixes this, but it comes back after awhile, so I suspect this is cache-related. We use Redis.

This is a pretty new Drupal 8 site that used the Lightning install profile. We use Panels/Panelizer for layouts. We have a bit of custom code in place (a few form alters, a few blocks, a few redirects, nothing particularly complex - but it's certainly possible there's something off in there).

Anyone seen this before or have troubleshooting suggestions?
Figured this one out, not particularly efficiently (never really found a good way to backtrace this), but got there nonetheless.

The issue was coming from the Custom Permissions module, which I'd incorrectly written off as innocent early on in troubleshooting since I use it on other sites without issue. Whoops.

That module lets you create permissions via a UI for any path you'd like. We had one in place that created a permission that was already defined by core (managing blocks -- accessing admin/structure/block). Removing this redundant permission fixed our problem here. (Uninstalling the module also fixed the issue.)

I'll post an issue in that module's queue if it's reproducible with a clean install.