Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.86
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e
Short description of error
I have a large scene with a vehicle which has an armature in it. When I press the space bar to play the animation of the vehicle armature I get different playback speeds depending where my mouse cursor is placed at the time I press the space bar. If the mouse cursor is hovering over the 3D Viewport I get 25fps but if I hover my mouse cursor over the Timeline and press the space bar I get 19fps. No other changes - just where my mouse happens to be when pressing the space bar.
Exact steps for others to reproduce the error
[Please describe the exact steps needed to reproduce the issue]
You need a heavy scene with an armature in it such that the computer just manages to achieve the desired fps. Then when you move the mouse cursor to hover over the timeline or graph editor or the dope sheet and press the space bar to start playback, the fps will be less than if you press the space bar when hovering over the 3D viewport area of the screen. If you have the mouse cursor over the Outliner or the Properties editor when you press the space bar you also get the higher 25fps playback.
[Based on the default startup or an attached .blend file (as simple as possible)]