Was this around the time right after “custom GPTs” was introduced? I’ve seen posts since basically the beginning of ChatGPT claming it got stupid and thinking it was just confirmation bias. But somewhere around that point I felt a shift myself in GPT4:s ability to program; where it before found clever solutions to difficult problems, it now often struggles with basics.
This is my guess as well. They have been limiting new signups for the paid service for a long time, which must mean they are overloaded; and then it makes a lot of sense to just degrade the quality of GPT-4 so they can serve all paying users. I just wish there was a way to know the “quality level” the service is operating at.