Glitchy drawings

I’m drawing on Harmony Premium and each time I draw, I get this weird glitch that flickers each time I draw a new line?
What could be going here? Is it Harmony or just my computer that’s the problem?

What’s your graphics hardware? Windows or Mac? Have you installed the latest video card drivers?

Try disabling “Enable Mipmapping on Bitmap Layer” on the OpenGL
tab of the Harmony preferences. Your graphic card probably does not
support this feature.