Downloading large files does not work in multi-threaded mode

Downloading large (350MB) files does not work in multi-threaded mode (for example, in Download Master ? westbyte). The file is downloaded to 99% and then does not go. Restart doesn’t help.
The situation is checked and on a clean test site.
Version Download Monitor – 4.4.14 (it was the same in older versions).

The client log is something like this.
The actual file is 328 MB (344,057,137 bytes).

GET /download/112/ HTTP/1.1
User-Agent: Download Master
Accept: */*
Accept-Encoding: identity
Referer: https://test01.test/download/112/
Range: bytes=344057136-
Cache-Control: no-cache
Host: test01.test

HTTP/1.1 206 Partial Content
Connection: Keep-Alive
Keep-Alive: timeout=5, max=100
expires: Wed, 11 Jan 1984 05:00:00 GMT
cache-control: no-cache, must-revalidate, max-age=0
set-cookie: wp_dlm_downloading=eyJkb3dubG9hZCI6MTEyLCJ2ZXJzaW9uIjoxfQ%3D%3D; expires=Thu, 13-Jan-2022 15:19:32 GMT; Max-Age=60; path=/; HttpOnly
x-robots-tag: noindex, nofollow
content-type: application/zip
content-description: File Transfer
content-disposition: attachment; filename="lineage-14.1-20211029-UNOFFICIAL-eagle.zip";
content-transfer-encoding: binary
accept-ranges: bytes
content-range: bytes 344057136-344057136/344057137
content-length: 0
date: Thu, 13 Jan 2022 15:18:32 GMT
server: LiteSpeed

the long-described solution to the problem helps – fix DownloadHandler.php:

line 554: ?$new_length = $range_end - $range;? -> ?$new_length = ($range_end - $range) + 1;? 
line 564: ?if ( $this->readfile_chunked( $file_path, $range ) ) {? -> ?if ( $this->readfile_chunked( $file_path, false, $range ) ) {?

first fix – allows you to complete the download
second fix – fixes the problem of broken files, otherwise large files are damaged.

why is this not in the official release?!