Task generated T-SQL shows unknown property IsMemoryOptimized
Converting comment to answer so as to close this question:

Most probable reason that error has been witnessed in SQL server 2014, could be you are not updated to the latest cumulative updates.


  unknown property IsMemoryOptimized


has been reported as bug, may not be somewhat similar to you're situation, but CU has been suggested.

However, for now, please try to make the changes using the SQL server 2008/R2 and see if that works.