No point in unescaping the expression also in suffixQuery() also 'cause it will exit sqlmap if the parameter value is a string hence injection payload starts with single quote (')

lib/core/agent.py

@@ -181,7 +181,6 @@ class Agent:
             return self.payloadDirect(expression)
 
         expression = self.cleanupPayload(expression)
-        expression = unescaper.unescape(expression)
 
         if comment is not None:
             expression += comment