Also seen a 2-week latency 10+ times increase of Gemini 2.5 Flash finetuned (= enterprise) model endpoints, again undocumented and unacknowledged, because they shifted all of their GPU capacity towards going "viral" on people generating slop artwork around Nano Banana Pro release.
So plenty of silent shenanigans do happen, including by the Big 3 on API endpoints. At the same time I agree with you that all those rumors of "degradation in code quality" are very much unproven.
I can’t speak to any kind of identifiable pattern but man that behavior drives me up the wall when it happens.
When I run into a specific task that starts to trigger that behavior, even a clean session with explicit instructions directing it to complete ALL sub steps isn’t enough to push it to finish the entire request to the end.