System Information
Operating system: Windows-10-10.0.19043-SP0 64 Bits
Graphics card: GeForce GTX 1060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 445.87

Blender Version
Broken: version: 3.1.0 Alpha, branch: master, commit date: 2021-12-13 00:03, hash: rB03015a9b222e

Short description of error
This is a bug that happens quite often both on Windows & Linux, as far as I've tested.
It's also related to the known issue of T92364.

In short, when click & dragging on thumbnails of the pose library tap in the sidebar, there is a chance that the click will pass through the menu and execute the active tool in the editor instead.
This happens very rarely on left click select but much more reliably when using right click select with the keymap option "Right Mouse Selection Action = Selection Tool".

Exact steps for others to reproduce the error

• Download the pose library demo file: https://www.blender.org/download/demo-files/
• Open the file and change the keymap options to the ones mentioned above
• Click & drag through the thumbnails a few times.