Resolved
The fix released has solved the issue, all systems should be operational now.
Monitoring
As part of the reorderable page actions last week we migrated pageActions into a new shape and removed old values. Our published content wasn't properly updated to no longer check the old values, and thus errored out because it was checking data that wasn't there (depending on what version of the customization object you were served, some sites were still using the old shape and thus functioned).
We're mitigating by properly checking both data shapes for the foreseeable future, until all sites are completely using the new format.
Identified
The issue affects some sites, resulting in Internal Server Error when visiting a site. We have identified a cause and expect to have a fix in near future. Not all sites are affected due to caching.
