Long Stalled/Blocking Time on big fileupload

Question

UPDATE 2: Stalled Problem solved

I'm using dropzone.js to handle file uploads to a shared hosting. Shared hosting is on NovaTrend. NovaTrend is using Litespeed.

In that try described here I uploaded 3 files inside one request with 400 MB. My upload speed is 10/Mbps.

Clientside I work with vue.js and serverside with Laravel 5.3.

PHP implementation

$file->storeAs('uploaded', Uuid::generate(4));

Dropzone.js settings

parallelUploads: 20,
uploadMultiple: true,

php.ini File looks following

memory_limit=512M
log_errors=On
max_execution_time=1300
max_input_time=1300
upload_max_filesize=750M
post_max_size=800M
register_argc_argv=On
upload_tmp_dir=/home/username/tmp/projectname

I know that it's possible to set the following code in .htaccess file to make sure that the scripts isn't canceled when upload big files which need alot of time.

<IfModule Litespeed> 
    RewriteEngine On
    RewriteRule .* - [E=noconntimeout:1]
</IfModule>

Now I have the following problem:

The request sent 6.2min is okay because 400 MB and 10/Mbps it's okay. And the Waiting (TTFB) I don't know, does copying the file takes so much time?

The Stalled Time is enourmous and I have no Idea were it comes from. I hope I understand it right but this error has nothing to do with server settings, or am I wrong?

Google Docs: Stalled/Blocking - Time the request spent waiting before it could be sent. It can be waiting for any of the reasons described for Queueing. Additionally, this time is inclusive of any time spent in proxy negotiation.

So I think of request is not sent so the problem is client side.

UPDATE 1

An upload with 2 files and size 150 MB works without the Stalled problem:

But another question is why it takes 2.5min for waiting (TTFB). The Request sent is again clear.