Freeze at folder listing

I have experienced mairlist freezing several times when I have to browse folders in database application. It happened when browsing folders in dialogs for music template creation, for example if I want to choose a directory to pick random music from.
I run multiinstance Mairlist. I have everything in 1 postgre database and music channels (instances) are separated into folders. I.e. there is one folder with 38 000 songs in over 3000 folders.
When using those dialogs, all folders are expanded per default and I find it hard to find correct directory, and after some time of browsing those folders, app freezes.

Attaching latest freeze:

Please try the latest 6.1 snapshot, we have replace the dropdown with a button and a separate selection dialog, which improves performance a lot when you have a large number of folders.