Cursor + Claude 3.5 Sonnet is doing very dumb things

For several days already I was noticing degradation in Cursor responses, to the extent that it couldn’t finalise very simple tasks (in a smart way). It definitely was able to accomplish such tasks in much better way previously. Then I noticed that I actually ran out my 500 monthly requests and got switched to so called slow requests. My question is if those fallback requests are only slower, or also dumber? I’ve read through the site and forum, I do not see a clear answer to this anywhere. I think it is understood that quality should be the same?