Anyone have a PSQUERY get corrupted in production?

On a couple of occasions, we have had a Query, created from Query Manager, stop working in production.  It times out, or gets an error message "Unexpected Signal Received".  The query hasn't been recently changed and has been working consistently for months.  When we open the query in Query Manager, we see weird, unprintable characters in the expressions and criteria fields.  But, when we look at the Query in App Designer, the query has the correct expressions and criteria.  We fixed the problem by updating the criteria with the values that are displayed in App Designer.  In other words, the