Error 204 Undefined - Help

We have worked hard on producing a PWA and we’re on the final stretch. The problem we’re having is that when doing a test at and using an emulated Moto G4 with Chrome, we are getting a bunch of undefined 204 responses in the waterfall. I am finding it almost impossible to debug since I don’t see it in dev tools and there is nothing actionable in the header requests. Initiator line is always blank “” although it appears it is looking for an image.

The app seems to function as it’s supposed to but obviously something is wrong. From document complete to fully loaded, these are causing an additional 1 second of wait time and it matches a lighthouse test for Time to Interactive. The site is and it is a wordpress 5.4 site.

Here is a copy of a recent report from

Any help would be appreciated. Thanks.

After months of going crazy over this, it turns out that WPT is the only site to notice and report. My site is setup as a Progressive Web App and I needed to specify additional apple-touch-icon sizes in the manifest. It’s an easy fix but bloody difficult to find since an undefined doesn’t tell you much.

Anyway, just replying to the thread in case some other poor bugger is spending months frustrated by this. Cheers.