The issue is easily reproduced with the following command: $ ab -n100 -c100 http://localhost/js/app.js
I typically see 1 successful request and 99 failures due to net::ERR_CONTENT_LENGTH_MISMATCH.
The js file in question isn't the only one effected, the error is also seen on our main .css file. The files in question are 1.29MB for the js file and 696KB for the css and we see the error the most against the js file. Rarely we've seen it against our fonts .tff file which is only 57KB and our images which are very small as they're either small logos or avatars. So the conclusion I've come to is that the size of the file increases the likely hood of the error occouring, and that it's of course only affecting static files.
Apache error logs show nothing helpful, and when reproducing the issue in a browser all you can see is the console throwing the error in question and the file loading with the end cut off at seemingly random points each time.
List of enabled apache mods:
$ ls /etc/apache2/mods-enabled/
access_compat.load auth_basic.load authz_core.load autoindex.conf deflate.load env.load headers.load mpm_event.conf negotiation.load proxy_fcgi.load reqtimeout.load setenvif.load
alias.conf authn_core.load authz_host.load autoindex.load dir.conf expires.load mime.conf mpm_event.load proxy.conf proxy_http.load rewrite.load status.conf
alias.load authn_file.load authz_user.load deflate.conf dir.load filter.load mime.load negotiation.conf proxy.load reqtimeout.conf setenvif.conf status.load
Apache version (latest):
$ apache2 -v
Server version: Apache/2.4.48 (Ubuntu)
Server built: 2021-07-01T19:15:28
