DFRobot 7 inch dsi screen fluctuating brightness

I have connected a DFRobot 7-inch DSI touchscreen to my raspberry pi 4  all seems to work OK..but

the screen occasionally seems to fluctuate in brightness. ie for just a second the screen gets a little brighter or darker.

Anyone else have a similar issue..?

I also discovered that when the pi 4 is attached to the back of the screen, wifi becomes disabled or very patchy.. The raspberry pi 4 needs to be away from the back of the monitor