Thank you for reporting a bug to Unity.
We have reviewed the issue carefully, and in this case, the team is unable to prioritize fixing this bug. There are a number of reasons we make this decision, including the impact and severity of the issue across our user and customer base, and the possibility that future plans may solve the problem in a different way, or that a workaround for the bug may be available.
Today we will be closing this case. Thank you again for taking the time to report this issue, and please let us know if there is anything else that changes the impact or severity of this issue.
The FBX file associated with this issue has a malformed DOM, and using the file with the official Autodesk FBX Review application has a similar outcome.
Whilst clearly not ideal behaviour for Unity, unfortunately we will not be prioritising this issue.