I use a system prompt that forces it to ask a question if there are options or if it has to make assumptions

I'm kind of amazed that even works. I'll have to try that. Then again, I've asked ChatGPT to "respond to all prompts like a Magic 8-ball" and it knocked it out of the park.

so I start a new chat frequently.

I do this as well, and totally forgot to mention it. Yes, I keep the context small and fresh so that prior conversations (and hallucinations) can't poison new dialogues.

I also will do the same prompts on two models from different providers at the same time and cross reference the idiots to see if they are lying to me.

Oooh... straight to my toolbox with that one. Cheers.