I recently got this question on my YouTube channel:
Without knowing the full details of the question, I suppose this person has set a lifespan which is more than 1 (the default option in Dialogflow is 5).
Ideally, you always set a context lifespan of 1 for all your contexts to avoid these kinds of issues.
Also, if you would like an intent to be ignored, you need to set an input context for that intent. In theory, an intent is always a selection candidate if you have not added an input context. So an important step in creating intents which can be “ignored” is to add an input context to that intent.