Rekordbox 5.6.0 (x64) crashes on (every) startup Win10Pro (1909) x64

I've installed the Rekordvox Version 5.6.0 (x64) on my Windows 10 Pro (1909) x64 and on every startup nothing happens. In Evenlog there is an "Application Error" entry with "rekordbox" (crash). I use no Hardware, this PC is the main library host.

Additional Info:
On another PC (very tiny Hardware specs; Intel i3 7100U, 16GB RAM, Intel HD Graphics 620, 500GB SSD) Rekordbox 5.6.0 starts perfectly well, but here I could not load my huge Library....)

The Versions 6 (6.5.1 + 6.5.3) works perfectly well.

BUT:
I need exact this version (5.6.0) to import my huge library (Playlists, Cue-Point, Loops, ...) from Traktor Pro 3.5.1 into Rekordbox! (I will not do all the work again.

I've read this post: https://forums.pioneerdj.com/hc/en-us/articles/205021519

0) Have you read the "READ ME FIRST" thread in its entirety AND TRIED THE SOLUTIONS THERE before posting:  Yes, I swear it!
1) Operating System:  Windows 10 (1909)
2) OS Type: 64bit 
3) rekordbox version: 5.6.0 (crashes)
4) Using LINK: No 
4b) LINK Connection method:---
4c) Using with CDJs: No 
5) Source Hard drive / Flash drive / SD card file system: none
5b) Connection type: ??? (just want to start rekordbox)
5c) Does the device have multiple partitions: ---
5d) If it's a flash drive, is it a U3 device: ---
5e) With what utility did you format the device: ---
6) Export Hard drive / Flash drive / SD card file system: ---
6b) Connection type: ---
6c) Does the device have multiple partitions: ---
6d) If it's a flash drive, is it a U3 device: ---
6e) With what utility did you format the device: ---
7) Have you scanned your files for errors: ---
7b) Have you scanned your drive for errors: yes (drive C, where rekordbox is installed)
8) Is rekordbox crashing at all:  YES
8a) If crashing, is it resulting in: no error, but in eventlog
8b) If not crashing, are there any error messages: ---
9) Are you able to repeat / reproduce the problem:  Yes
9a) If yes, can you do it consistently:  Yes
10) Does the problem occur with one specific song: ---
10a) If yes, please post a link to it: ---
11) Any other notes regarding your setup only: ---
12) Provide as much detail of the issue here:

MB: AsRock Taichi Z390
CPU: Intel i9 9900K (no overclocking)
GPU: Sapphire Radeon 580 8GB
SSD: Samsung NVMe 980 Pro 1TB (Drive C)
OS: Windows 10 Pro x64 (1909)

Downloaded the Rekordbox V5.6.0 (Win, x64) from Pioneer Original Website.

Eventlog: (Error Message)
###
Protokollname: Application
Quelle: Application Error
Datum: 08.09.2021 17:34:46
Ereignis-ID: 1000
Aufgabenkategorie:(100)
Ebene: Fehler
Schlüsselwörter:Klassisch
Benutzer: Nicht zutreffend
Computer: ---
Beschreibung:
Name der fehlerhaften Anwendung: rekordbox.exe, Version: 5.6.0.0, Zeitstempel: 0x5cc017d7
Name des fehlerhaften Moduls: rekordbox.exe, Version: 5.6.0.0, Zeitstempel: 0x5cc017d7
Ausnahmecode: 0xc0000005
Fehleroffset: 0x00000000004faf89
ID des fehlerhaften Prozesses: 0x664c
Startzeit der fehlerhaften Anwendung: 0x01d7a4c70da43df3
Pfad der fehlerhaften Anwendung: C:\Program Files\Pioneer\rekordbox 5.6.0\rekordbox.exe
Pfad des fehlerhaften Moduls: C:\Program Files\Pioneer\rekordbox 5.6.0\rekordbox.exe
Berichtskennung: 66cf8673-b58c-4de9-baf9-ca18332ea2ad
Vollständiger Name des fehlerhaften Pakets:
Anwendungs-ID, die relativ zum fehlerhaften Paket ist:
Ereignis-XML:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Application Error" />
<EventID Qualifiers="0">1000</EventID>
<Level>2</Level>
<Task>100</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2021-09-08T15:34:46.710677500Z" />
<EventRecordID>229608</EventRecordID>
<Channel>Application</Channel>
<Computer>---</Computer>
<Security />
</System>
<EventData>
<Data>rekordbox.exe</Data>
<Data>5.6.0.0</Data>
<Data>5cc017d7</Data>
<Data>rekordbox.exe</Data>
<Data>5.6.0.0</Data>
<Data>5cc017d7</Data>
<Data>c0000005</Data>
<Data>00000000004faf89</Data>
<Data>664c</Data>
<Data>01d7a4c70da43df3</Data>
<Data>C:\Program Files\Pioneer\rekordbox 5.6.0\rekordbox.exe</Data>
<Data>C:\Program Files\Pioneer\rekordbox 5.6.0\rekordbox.exe</Data>
<Data>66cf8673-b58c-4de9-baf9-ca18332ea2ad</Data>
<Data>
</Data>
<Data>
</Data>
</EventData>
</Event>

###

If someone could help, it would be great! THX :-)