1. Initially I was trying to restart the unsteady FSI from the steady flow solution over the initially undeformed structure. I noticed that the case diverged when I tried to use 2nd order dual time-stepping and the case worked when I used 1st order dual time-stepping.
2. Then I encountered a new problem when I tried to restart the case from the FSI solutions after 1900 time steps and it diverged. I tried the restart files of time iteration 1890 and it still diverged without iterations.
3. Surprisingly, when I tried to restart using the restart file from time iteration 10, iterations started without an immediate divergence.

Please advise on what could be going wrong.
Thank You
Sangeet

I have attached the case folder with all required restart files.
testing.zip