Please upgrade to latest 5.1.15 with command
/usr/local/lsws/admin/misc/lsup.sh -f -v 5.1.15
There is a related bug introduced in earlier build of 5.1.15, fixed.
It is probably because cPanel killing LiteSpeed, then start up Apache.
We need to find out what operation trigger Apache being started, and why?
Can you give us temp root access to the server having this problem? Just open a support ticket.
There must be Apache being started temporarily and crashed. if you look at the logging style, the timestamp, litespeed generated log entries are in completely different format.
Are you using cPanel?
Looks like it is crashing, can you locate the core file?
If you installed 5.1.15 before Sunday afternoon, please do another force update to get the latest 5.1.15 package.
Please change debug level to HIGH and do the same test. just track related log entries with the IP and port combination.
You should see log entries at the end that connection was closed no matter what is the reason.
The current log shows it is still trying to send remaining file, no close.
For #1, you need to check if there is any bandwidth throttling configuration, using mod_bw style configuration, it has special directive for limiting large file download. Also, make sure your server does not set
https://www.litespeedtech.com/docs/webserver/config/tuning#sndBufSize
it should be...
I think you need to turn off static file expires, so the browser wont cache the css file. By default, LiteSpeed has expires setting enabled.
https://www.litespeedtech.com/docs/webserver/config/general#enableExpires
Are you using rewrite rule to control lscache?
You should add a rewrite condition to test for content-range request header, do not enable cache if present.