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I’ve noticed the same. It was especially frustrating for me because I used GPT-4 for extremely complex math and coding tasks. So, now GPT-4 is unable to solve many tasks that have been successfully solved by the previous version (before the May update), I’ve tested on previous prompts (which were saved in the history) with lots of attempts to reproduce the previous solutions. That’s why I’ve stopped the Plus subscription. I’m waiting for clarification of this situation from OpenAI. I loved early GPT-4 and it helped me a lot, but now I feel tricked. 
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