The Platform API does not find a document tray/filecabinet reliably

Behavior:

The Platform API does not find a document tray/filecabinet reliably.

Cause:

A possible cause for this behavior is that there are multiple document trays or filecabinets with a similiar or even an identical name. (Every user has a document tray named "Inbox" and the admin-user sees all of them, for example.)
If you want to get the the object in your Platform-tool using the name, it can happen, that you get the wrong one or non at all. This depends on the method, you are using in the code.

Solution:

In your Platform-Tools you should always use the ID to get the correct object. This ID is unique in your whole system and therefore a mix-up is impossible.