I tried to reproduce it, but failed, both the lock/unlock of a large folder, and locking folder while there is a document open.
From my experience with Espionage, the speed at which the folder unlocks/locks does not depend on the size of the folder, at least not in a visible way.
I do recall that sometimes when you try to mount a big disk image, like OS X install disk image or such, there is a window saying "verifying disk image", so maybe this is the time during which the folder is in this undefined state. I will check with devs if this is possible.
For the folder allowing to lock while a document is open, if I try that, I get a notification with OS error -47 which is the equivalent of "file busy" error.
Now, this is of course if there is a file open. You did not say that there was an open file, but that the Mail was running. I can hardly imagine that a running Mail does not keep any single file open, but then again, all is possible in some rare circumstances.
So what I would kindly ask you:
- re big disk image, I will check with devs about details, and you please try to reproduce it again, if you manage, then please open the console application, select system log and later "all messages" and see if there are some recent espionage related lines.
- re possibility to lock the folder while a file is open, can you please test with some other folder, other then Mail. If you do manage to reproduce it, then let me know. If you can reproduce it with mail, then while the folder is locked and Mail running, run the following command from the terminal
lsof | grep -i mail >lsof.out, and send me the lsof.out file.
Thanks
Zsolt