@nasser: you're describing standard kindle framework behavior, that CM doesn't directly have any impact on, it just makes use of what's implemented but not public, so, yeah, there are a few kinks in how the framework actually deals with nested collections ;-).
Mostly minor graphic issues like you experienced, especially with how the 'Back' action is handled from a nested collection.
EDIT: What I mean to say is: CM doesn't have any control over how the framework actually decides to display/navigate nested collections, and, yes, there a few minor graphics glitch in some circumstances

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