I'm finding the same with ChatGPT recently since the 5.6 release. Not as bad though, but sluggishness at times, harness churn (creating bugs and crashed), and occasional availability issues that cause me to downgrade to 5.5.
It's gotten to the point where I dread a new model release from these companies because it's guaranteed to be disruptive! I assume the pay per use API is less impacted.