Unreal 4.21 - Click play and resize window stops Niagara particles from working, why?

For some unknown reason Niagara particles stop working if i click to resize window after click play in UE editor, basically when i click play, a “new editor window (PIE)” appears, if i play with the actual size of the screen (game preview stang alone), no problems at all, all particles work OK, but if i click the maximize button to make the window full screen, particles stop working, also if i use multiple screens and i move the window to another screen, particles stop working too. Even if particles do work in default screen size, after click maximize, they stop working. Sometimes if these paticles are composed of several emitters, 5 for example, 2 might work, and the other 3 don´t, very weird.

If i close window and click play again in default window size, everything Works perfect.

Why is this happening to Niagara, this never happened with previous versión of UE.