I just spent a couple of hours trying to figure out why one of my images (placed Illustrator file) was pixelating in EPub output. The same image is placed in 6 places, and only in three of those instances was the output incorrect. Image is identically placed in all six instances (size and scaling), the link is valid (not missing), and all export settings were correct. As a last resort troubleshooting this, I realized that in the three locations that were pixelated, the display setting for those three was set to Typical rather than High Quality. I set them to High Quality and lo and behold the export was fixed.

I've never seen this happen before and I know that it's not supposed to happen at all, but in this case it was definitely the problem. I'm assuming it's a bug, but whether it's repeatable or not I don't know. Unfortunately, I can't send the file in question for analysis because the content is sensitive and proprietary but wanted to report it anyway in case others are having the same problem.

I'm using InDesign version 17.3 on Windows