have you migrated to Classic FDM or FDMEE?
My customer had similar issue with AftExportToDat script which triggers Cal Manager Command line Launcher utility that runs four business rules on Essbase and finally it runs forever at Export Step.
We ended up applying Essbase RTC 106 patch which resolved the issue and the release was 188.8.131.52
Now in your case - did you migrate to FDM or FDMEE ? Also does AftExportToDat script invoke other components utilities ?
Possible to post here the FDM logs for experts' review ?