Mixed metaphors are different metaphors occurring in the same utterance , especially the same sentence, that are used to express the same concept.
Mixed metaphors often, but not always, result in a conflict of concepts.
The following sentences illustrate a mixture of the argument-as-journey and argument-as-container metaphors. The first three sentences are acceptable; the last two are marginally acceptable.
Lakoff, George, and Mark Johnson. 1980.Metaphors we live by. Chicago: University of Chicago.