Hi there. First, very useful and well supported plugin. Keep up the good work.
With Custom Post Widget and the Post Type Switcher plugin activated, editing a content block causes the post type to be switched to post rather than content block. The initial save of the content block works fine; it's only on the 2nd update that the post type gets unintentionally switched. Deactivating Post Type Switcher causes Custom Post Widget to function normally (ie, you can edit and re-edit content blocks).
I'll flag the plugin author of Post Type Switcher to this post in case he's aware of anything.