Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: Quadro 2000/PCIe/SSE2 NVIDIA Corporation 4.4.0
Broken: version: 2.80 (sub 66), branch: master, commit date: 2019-05-16 12:17, hash: rBe60890075b37
Short description of error
After linking Collections with 'Instance Collections' unchecked, 'Make Proxy' for Armatures will create the Proxy within the linked Collection (which should not be editable). Since the linked collection is still immune to other actions, moving the new Proxy out of it creates a duplicate in the outliner.
Blender becomes unstable and may crash at any time the new Proxy is edited; especially on loading a new file though. Saving the file and reopening it within a new Blender instance will fix the issue (since the linked collection is loaded in its original state).
Exact steps for others to reproduce the error
Example: Open the "shot.blend" file and create a proxy for Armature.