Trouble with color 'banding(?)'

Made with 16bit RGBA image and loaded as truecolor image.

But, If I add image effects “Bloom” or “Vignetting”, It shows like this.

I couldn’t get any good solution. How am I supposed to do?

16279-hate.png

I got the solution! It was because of “Glow Effect”, the old image effect.

Removing and changing to “Bloom Effect” and turning on “HDR”, the phenomenon disappeared.