Problem is that by default ChatGPT has the “Reference chat history” option enabled in the Memory options. This causes any previous conversation to leak into the current one. Just creating a new conversation is not enough, you also need to disable that option.
This is also the default in Gemini pretty sure, at least I remember turning it off. Make's no sense to me why this is the default.
That seems like a terrible default. Unless they have a weighting system for different parts of context?
Only your questions are in it though