I see. I wasn't sure if it was and FBX you imported and then was trying to export again.
In this case, I'd try and ENU reset first. If that fails, maybe a reinstall. It sounds like a local issue though. I'm sure millions of FBX files are expored every day using Max and if it were a bug there would be 1000s of people screaming about it.
Rob Holmes

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3ds Max (2023-2026), V-Ray 7, Ryzen 9 9950X3D Processor, DDR5 128MB, Gigabyte Aorus X870E Master motherboard, Sabrent Rocket NVMe Gen5 M.2 drives, NVidia RTX 4090, Space Pilot Pro, Windows 11 Pro x64, Tri-Monitor, Cintiq 13HD, Windows 11 x64
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