I suspect you are interacting with LLMs in a single, long conversation corresponding to your "session" and prompting fixes/new info/changes in direction between tasks.

This is a very natural and common way to interact with LLMs but also IMO one of the biggest avoidable causes of poor performance.

Every time you send a message to an LLM you actually send the entire conversation history. Most of the time a large portion of that information will no longer be relevant, and sometimes it will be wrong-but-corrected later, both of which are more confusing to LLMs than to us because of the way attention works. The same applies to changes in the current task/objective or instructions: the more outdated, irrelevant, or inconsistent they are, the more confused the LLM becomes.

Also, LLMs are prone to the Purple Elephant problem (just like humans): the best way to get them to not think about purple elephants is to not mention them at all, as opposed to explicitly instructing them not to reference purple elephants. When they encounter errors, they are biased to previous assumptions/approaches they tend to have laid out previously in the conversation.

I generally recommend using many short per-task conversations to interact with LLMs, with each having as little irrelevant/conflicting context as possible. This is especially helpful for fixing non-trivial LLM-introduced errors because it reframes the task and eliminates the LLM's bias towards the "thinking" that caused it to introduce the bug to begin with