Take a look at the sentence again:
On school mornings, Rachel can sleep through anything, even
with the alarm clock buzzing or
when Mom bangs on the bedroom door.
When you list grammatical items, you must use parallel structure. Here, you have one prepositional phrase, with the alarm clock buzzing, and one subordinate clause, when Mom bangs on the bedroom door, wrecking the parallelism.
To fix the sentence, you must give both items the same grammatical form. For example, you could change with the alarm clock buzzing to when the alarm clock buzzes.