So I bought Displayfusion a few days ago for livestreaming, and I found that League of Legends always flickers on my major monitor once the game starts loading under windowed fullscreen mode.
The weird part is that it doesn't flicker before the game starts loading, and it doesn't stop flickering until I change it into fullscreen mode.
Even more weird, once I set it into fullscreen mode, it stopped flickering; then I could switch back to windowed fullscreen and it works fine, no flickers whatsoever. But when I finished a game and starts another, it starts flickering again.

I've tested under various environment and hardware, the only way to solve it is to turn off displayfusion...

Is this a known bug or is it caused by some wrong settings on my end?

Here's my PC:
CPU: Intel Xeon 1230V2
HDD: 128G SSD
GPU: MSI GTX 660Ti / ASUS GTX 770 (tested both, both flickers)
Monitor 1: Acer P246H 1920x1080
Monitor 2: LG W2252TQ 1680x1050

Thanks for replying.

Hey I just disabled title bar button and the flicker is gone!

So that's the reason why it's flickering, maybe displayfusion tries to apply the button and caused the flicker.

Thanks for replying!