The Case Gold exported from Fluent 18.0 and 18.1 contains a bug. If your model contains multiple fluid parts, it is possible that the value of the variables is artificially set to zero at the boundary between parts.
The Fluent development team has already identified and fixed the issue. The next release of Fluent (18.2, scheduled for Fall 2017) will contain the correct Case Gold exporter.
If you are running Fluent version 18.0 or 18.1, please consider using an older version of Fluent for exporting the dataset in Case Gold format. Failing that, you can use the native Fluent .cas/.dat file reader from within the EnSight File -- > Open Dialog.