Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 388.43
Broken: version: 2.80 (sub 57), branch: master, commit date: 2019-04-14 19:18, hash: rB860a9f979d60
Short description of error
In the Graph Editor, when clicking on Channel - Extrapolation - Make Cyclic, the frame rate drops a lot.
Exact steps for others to reproduce the error
In pose mode, select all bones, go into the graph editor in order to make all the animation cycle. Select all curves, go to Channel - Extrapolation Mode - Make Cyclic.
Everything is cyclic as wanted, except that the frame rate is divided by 5 on my computer. It makes it very impracticle to edit the curves and see the result in real time.
What makes me think this is a bug is the fact that one simple fix I found is to simply close the graph editor window, or change it to another panel. Then the frame rate is back to normal and the animation cycles just fine.