Hi, Thomas. Just to check things out, I chose a group that contained 7,708 items (groups and documents) and exported it using Files > Export > Files & Folders to a target folder.
The log file showed that one file failed to export, a JPEG file damaged during editing.
Then I created a new database and imported the exported materials into it using File > Import > Files & Folders. The new database showed 7,707 items (groups and documents). The content included plain and rich text, PDFs, HTML, WebArchives, “unknown” file types and URLs (to external Indexed files). All of the metadata, including URLs of HTML and WebArchive documents, Paths (to indexed documents and to the files stored in the internal Files folder) and so on were complete.
Everything worked properly.
What can cause problems? A variety of possibilities: damaged files, something as simple as lack of disk space to hold the new database, or operating system and disk directory errors.
If you have installed haxies or other hacks on your computer, including third-party input manager plugins or QuickTime media plugins, they may have been poorly written or have ‘broken’ after an OS update. Hacks to the operating system are probably the most common cause of flakiness and instability on Macs. Most developers of OS hacks lack Apple’s resources for testing and quality assurance. Even ‘simple’ add-ons to Safari – especially if they involve an input manager plugin – can have unforeseen effects resulting in errors. A hack such as ShapeShifter is pretty much an unqualified disaster, judging by the problems it can cause.
Personally, I find the convenience of a rock-solid computer saves me more time and effort than the convenience or time-saving that might be promised by some of the add-ons to the operating system. So I keep OS X in pretty stock condition.
Another source of problems is failure to keep the operating system and the disk directory maintained. I run routine preventive maintenance about once a week. A utility such as OnyX (donation-ware) or Co*cktail (ignore the asterisk - shareware) can help keep the computer clean of problems such as possibly damaged cache files and so on. I run DiskWarrior 4 about once a month to clean up and optimize the disk directory.
To the extent that you install things that modify the performance of the operating system or applications you increase the risk that errors can develop. If you do this, be careful and watch for problems. Keep such hacks updated, at the least. Remove anything that causes data loss or costs you time and effort to correct problems.