I am sorry to hear this. You may try:
1: copy all object but not the FDTD , and then paste to a new project, add new FDTD region and modify the setting.
2: if it still does not work, you may need to restart your computer.
3: You may also install the newest version.
A note for your simulation file: make sure that waveguides extend outside of PML (left side).
If the problem perisits, please send us an email for support, attach your file, and mention this post.
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