Red bar on the right side of the Program Monitor

It looks like a gpu render glitchy. Try restarting and resetting Premiere (if it bothers you)

Might be a display glitch. Try changing the resolution of your program window from 1/4 to full and see if it goes away.

Or change the size of your program window - drag the borders of your program window (the blue edges)  to change the window size and see if that makes it go away.