Operating system: Linux-5.3.0-42-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 435.21
Broken: version: 2.83 (sub 13), branch: master, commit date: 2020-04-10 21:07, hash: rBa8d139ca2002, 2.82a
Short description of error
You have a parent-children objects and you want to move them to another collection via drag'n'drop. You select the parent, do select hierarchy, drag by any of the selected object into another collection and only the selected is placed there. BUT on the second iteration of the process after undo it works properly.
This issue occurs only after the "select hierarchy" operation. Regular multiple select with the shift button works correctly.
And one more thing. It's more logical to drag by the parent and get the hierarchy moved automatically without the "select hierarchy" operation. But I think you know about it and I saw a ticket about that I guess.
Exact steps for others to reproduce the error
Open the attached file
Deselect all objects
RMB on the suzanne in the outliner, select hierarchy
Drag by the suzanne into the upper collection
Only Suzanne got moved
Drag by the suzanne into the upper collection once again
Now all the hierarchy got moved