Overload GPU with low fps - come and go

[orppang]

Hi expert,
I am using a MSI GF65 (i7-9750H) thin laptop , with GTX1660Ti, 16GRAM. My OBS behaves differently from time to time. Sometimes it is in good shape like 1920 x 1080, 60fps, 4000kbps, all green no dropped frames. I can stream out smoothly in one to two hours. But all in a sudden the fps dropped to 6 to 7 fps, CPU was only at 10%, except the GPU suddenly boosted to 100% in red. I did not turn on any game or graphic card driving software in both scenerio. I already run the OBS in admin right, and turn off all game mode/capture...etc. When the time of slow down, the fps will not go up again even I apply 720p /30Hz/2500kbps. I have no clue why my OBS is so moody. But the OBS can behave normally in the next day, this problem come-and-go day by day or hour-by-hour, it is quite frustrating. Do you have a solution?

 

[orppang]

Oh, I noted the reason of the drop in fps. My setup : My laptop is connected with two external monitors. When the OBS software is displayed on any of these external monitors, it works excellent 1080/60fps/4000kbps without frame drop or fps drop. But when I dragged the OBS software screen into the laptop own screen, the fps dramatically dropped. I guess it is related with the graphic driver effect on the native screen and OBS program. Although this cannot be fix, I can now live stream with OBS on second screen at 60 Hz.