Printing problem: resonant frequencies

Bambu Lab X1 Series
1

I printed an object twice with success, but the next two attempts failed with stringing. In one video, I could see the print tilting a little bit, as if the extruder was hitting the print. I am getting a message about how the resonant frequencies have changed, and to check the carbon rods. I expected to see a dirty nozzle, but the nozzle is clean, as are the rods. Please see the pictures. What should I do next, please?

Jon

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2

I recalibrated, after which the next print went fine. Fingers crossed as I attempt two more of the same.

3

I managed to get two more prints out, but there was one more unexplained failure. Not as reliable as my Prusa, but I’ve not used the X1 as much as the Prusa.