when previewing content in admin, if the siteaccess selected is in legacy mode, the kernel/content/versionview.php will cause the language cache to be cleared.
in a high load environment (with heavy editorial actions) previewing the content causes these errors:
the deadlock is caused in the versionview.php module, at:
this line was used to clear only in-memory languages before the language cache was introduced.
deadlock is not reproducible in a test environment, but we can check that executing a preview as described deletes the file, and generates a new one without any difference.