FBX 2019.5 (file version 7700) introduced a new number of "ktimes" per
second to more accurately support some animation frame rates. The new
value is an opt-in until FBX version 8000, where it should then become
the default.
The importer will now look for new the header version and flag
specifying to opt in to the new FBX_KTIME value.
The exporter is unaffected because it always writes an FBX version 7400
binary.