An Avalon item is created every time you choose the Create menu even if you do not associate any media or metadata with the item. These Avalon items will only be viewable by Collection Staff because they receive access status of "Collection Staff Only" by default. Avalon items can be deleted individually.
The poster images may have a strange aspect ratio when in full screen mode. This does not affect video playback which retains the correction dimensions.
There was a typo in matterhorn's config file etc/encoding/avalon.properites. Go to your matterhorn's etc/encoding directory and run the following:
wget https://raw.githubusercontent.com/avalonmediasystem/avalon-felix/release/3.3.0/etc/encoding/avalon.properties -O avalon.properties
No restart is needed.