CSS HTTP/2 Push get 503 http code error with openlitespeed server

I have one wordpress installation issue that when I enable "CSS HTTP/2 Push" feature from lscache wordpress plugin, the site get 503 error from openlitespeed server (I am suing 1.6.10-1, but tried also with 1.6.11.-1 and 1.6.12-1). The only log that I get with debug mode is:

```bash
2020-04-27 19:56:12.075803 [NOTICE] [xxx.xxx.xxx.xxx:55550#xxxxxxxxxxx.xxx] oops! 503 Service Unavailable
2020-04-27 19:56:12.075818 [INFO] [xxx.xxx.xxx.xxx:55550] Content len: 0, Request line:
GET / HTTP/1.1
```

/wp-admin continue working normally.

No file or test is named in the report. Start by reproducing the issue with CSS HTTP/2 Push enabled on OpenLiteSpeed 1.6.x, inspect the available debug log, and compare normal requests with the failing GET /. Done means the setting no longer produces a 503 while /wp-admin continues to work.

Written by the indexing model from the issue text.