Switching from Apache to LiteSpeed (Issues)

Hi all,

I'm testing LiteSpeed but have come across some errors that cannot resolve:

1. Using Xenforo software, it seems that there's an issue with CSS files being rendered. The errors shown are similar to this:

'Errors occurred when rendering CSS:\A * public:extra.less: ParseError: Unexpected input in public:extra.less on line 11, column 1 (on or near line 11)\A 8 | @block-noStripSel: ~.block-container:not(.block-container--noStripRadius);\A 9 | \A 10 | // HELPERS\A *11*| @zIndex-1: 1 * ();\A 12 | @zIndex-2: 2 * ();\A 13 | @zIndex-3: 3 * ();\A 14 | @zIndex-4: 4 * ();';
There's no PHP error, no error on browser console. I cannot find any other error to explain this. As soon as I switch to Apache or nGinx, this does not happen. I discovered this old thread that is similar:

XenForo bug with Litespeed | LiteSpeed Support Forums (litespeedtech.com)

But as far as I can tell this issue was resolved.
The reason I'm opening a thread here and not on Xenforo is that this only happens with Litespeed.

Where could I look at to find the actual problem?

2. Using Joomla software, there are certain AJAX request that simply fail. Again, this is hard to track down. Perhaps related to first problem?
As soon as I switch to Apache or nGinx, everything is ok. The problem is only with Litespeed. Same question goes here, where should I look at to track down the issue? (no php error here either).