Are you getting severe entries in any particular queue? Can you provide more information. Usually the queue entry details shall provide you more information on the error.
There are multiple reasons why you would see a severe entry in propagation queue, for instance if an object on which a particular workflow process is initiated gets deleted , you will see a severe entry in the wfpropagation queue.
You can execute the QueueAnalyzer report to check the error in the entries, following article should help you: