Operating system: Linux Mint
Graphics card: GTX 780
Broken: 2.80, d59c4c9d61a, 2018-12-05 03:23
Worked: 2.79, (somewhat of a comparison considering groups instead of collections....)
Short description of error
When a linked collection containing another linked and posed armature is in a scene and undo(ctrl+z) is used the armature pose resets its position.
The same scenario in Blender 2.79 using groups (instead of collections) does NOT have this behaviour.
Exact steps for others to reproduce the error
In order to reproduce this behaviour you need at least TWO files. One to represent an asset and one an environment. A third file is used to link in the collection from the environment file. This reproduces standard production procedures where environments with linked assets would be linked into a shot.
Create a rig asset (one bone armature will do) and put in collection. Save file as asset file.
Create a second file and link in the asset collection. Proxy the asset rig and edit the pose into a new position. Save file.
Link in the environment file into a new file. Do anything else (e.g. create a plane and move it). Hit undo. The asset rig will reset its posed transforms.