A couple of behaviors indicate that there may be a change. They are now three weeks later than the previously two years, and the birds’ pattern of nest attendance is different. The birds appear to be "figuring" out their way through the nesting process, whereas in the prior two years they were extremely efficient. Finally, after a nest failure (last year), nest switches are common.
I will be interested if you are able to do a comparison.
Keep up your amazing observations. What a great group of biologist you all are.