WebGL occasional incorrect header check

He guys.

We have our webgl game hosted on IIS with configuration as set below:

<remove fileExtension=".mem" />
<mimeMap fileExtension=".mem" mimeType="application/octet-stream" />
<remove fileExtension=".data" />
<mimeMap fileExtension=".data" mimeType="application/octet-stream" />
<remove fileExtension=".memgz" />
<mimeMap fileExtension=".memgz" mimeType="application/octet-stream" />
<remove fileExtension=".datagz" />
<mimeMap fileExtension=".datagz" mimeType="application/octet-stream" />
<remove fileExtension=".unity3dgz" />
<mimeMap fileExtension=".unity3dgz" mimeType="application/octet-stream" />
<remove fileExtension=".jsgz" />
<mimeMap fileExtension=".jsgz" mimeType="application/x-javascript; charset=UTF-8" />

Seems ok, right? But once in a while we get an "incorrect header check" error. I included the code above cause most related forum posts point to config.

Looking at where in the unityloader.js file the error is shown give me this:

if (n.flags = 0, n.head && (n.head.done = !1), !(1 & n.wrap) || (((255 & f) << 8) + (f >> 8)) % 31) {
e.msg = "incorrect header check",
n.mode = ce;
break
}

Now, I can't make heads or tails out of this but maybe someone else can. Who can explain me the 'if' statement here? Thanks in advance...

 

My reading of that suggests either n.wrap is an odd number or your failing the checksum like test of f (that the shifted bits aren't evenly divisible by 31)

 

Ok, thanks for that. Any thoughts on what that means? I can think of checksums in way that downloading the content could have been interrupted or something like that. But what about the n.wrap thing?
Already tweeted #emscripten to see if someone could give me some insights as well. Thanks!

 

I don't use the target, the excerpt you've shared is obviously not enough to make any guesses about why n.wrap has to be positive/divisible by 2.