Why Does ChatGPT Plus Not Process Full Transcript/report of ~10k tokens


I’m notice that when i upload a full youtube transcript or a long report to summarise, ChatGPT Plus (using GPT-4, not sure if Turbo) only processes around the first 3000 tokens of the uploaded transcript.
The resulting output maybe around 800-1000 tokens.

Why is this the case, as i thought ChatGPT plus currently uses Turbo, which has 128k token input limit?

When i asked the GPT to process the remaining parts of the transcript, it either says that is the end or hallucinates.

Is there a different token limit?
If it is an issue with the output limit, how can i ask it to prompt me to continue?