TYPO3 Core

DataHandler does a lookup in sys_log table after it performed
its operations to find relevant error entries for the current request.

It determines relevance by looking for entries with the same
timestamp as $GLOBALS['EXEC_TIME'].

However error log entries are written using time(). Now if the
DataHandler operations take longer than one second, or the log entry
is written directly before a next tick, it can happen, that errors
will not be detected during the lookup process.

Since such errors are exposed to the user, it can happen that an operation
fails, but the users will not be notified.