RTK to WAAS you will have line shift. I’d say you have been very fortunate if WAAS has always lined up that closely in the past. I did a little testing a couple days ago and I was seeing 3-4’ difference between MNCORS and WAAS at that time.

The solar storm this spring caused a lot of issues with GNSS of all brands. It was spotty, the exact same systems 20 miles apart could be working fine and having issues at the exact same time.

Put your RTK receiver in the combine and see if the lines line up as they should.