GPT-4 Quality decreased in the last 2/3 days?

after the update in the gpt creator system, I am experiencing a drastic downgrade of the performance of chatGPT. Some answers are not only incorrect, but also in some cases, totally out of the topic.
And there are some logic mistakes that remind me the first chatgpt 3.5 of one year ago.

the combined_data.csv I have uploaded is a dataset containing beast cancer data. I don’t know this custom GPT I have created , about which dataset is referring to.
A mixing of gpts machines? Maybe a dataset of someone else ?
seems impossible to think about an allucination, because in a previous answer it answered correctly about the same dataset.