Atom editor - different colored blocky background for dark themes

Description

This problem appears on Atom 1.32.1 under Ubuntu 18.04 in atom --safe mode. Enable a dark theme and start typing text, and the background alters between dark black, and dark grey, in large blocky chunks. Looks like an Atari 2600 game.

Expected behavior: One consistent background.

Actual behavior: See this picture. How do I escape this bug?

_{(source: discourse-cdn-sjc1.com)}