as I've said many times in the past, collective.cover is not supported in Plone 5 and will not be supported until somebody wants to pay for that or somebody wants to fix it.
we're using it in hundreds of Plone 4.3 sites and is working very well, very stable and with configurable general tiles that reduce the need to create specialized ones.
latest release fix a nasty bug that was causing exponential growth of object size when using versioning (and plone.app.iterate) and lots of modifications on the layout:
thank you very much, I have updated the list of pending issues:
we're to make a huge refactoring of the static resources using @rodfersou ideas before the end of the year, that will solve some of the JS issues, I guess.: