Just found a bug: when I edit an existing image to correct a thumbnail (say, when I want the thumbnail to show person's head only) and follow this steps -
1. EG > All folders > some folder > some image
2. Click ‘Edit Image’ under the image itself
3. In ‘Thumbnail Settings’ select ‘Thumbnail’
4. In ‘Image Crop’ section set Aspect Ratio 1:1
5. Holding down Shift button select the area you want to be your thumbnail with the mouse.
6. Click Crop (the very left icon on the tools panel)
7. Click Save
the new thumbnail is created: /albums/some_folder/some_image/_cache/_cache/some_image-e1369825962584-150x150.jpg
Problem is the double /_cache in filesystem and single one in db, so it appears as missing/broken thumbnail.
This doesn't happen with images uploaded as native WP media.
WP is 3.5.1, EG is 0.1.2 updated to develepment version.