What causes a form to close on it's own?

[ALX]

In a complex arrangement of various modal and non-modal forms, the process of minimizing and / or hiding certain forms causes some of them to close automatically... (or under VB's control). What are the conditions that would cause a form to close without being programmatically coded to do so?

 

[Lotok]

An exception?
Possibly also out of scope?

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