I have a large RM8 DB (over 500,000 people). When I attempt to copy a subtree from this to another DB, by dragging an ancestor to the new DB and selecting copy descendants and spouses the operation fails after appearing to write a few hundred people. I See a popup: Unexpected Error Invalid floating point operation. At this time the progress bar shows People: 430, Families: 150, events:1970, Sources: 190, Citations: 250, Repositories and witness:0 and Final Progress: 0%
It’s best to open a support ticket with a backup of the database for testing. If you haven’t done so already run the Database Tools under File, Tools.