[SOLVED] USB-file-transfer and adb sideload not working

I have a One Plus 6T. When I got it 1 year ago, I flashed the newest firmware from the official One Plus page (https://www.oneplus.com/de/support/softwareupgrade/) via fastboot in both slots and then installed LinageOS 17.1 for fajita. Now 18.1 is available since some time and I wanted to upgrade. The official page suggests using adb side load (https://wiki.lineageos.org/devices/fajita/upgrade) When going through the steps I noticed two symptoms:

USB-File transfer is not possible.
ADB does not recognize my device when it is in file transfer mode (it does work for USB-Tethering, MIDI and PTP)

I also see sideload failing:

C:\Users\user\Desktop\platform-tools>adb sideload C:\Users\user\Downloads\lineage-18.1-20210812-nightly-fajita-signed.zip
adb D 08-15 22:11:43  6228 14160 adb_trace.cpp:187] Android Debug Bridge version 1.0.41
adb D 08-15 22:11:43  6228 14160 adb_trace.cpp:187] Version 30.0.3-6597393
adb D 08-15 22:11:43  6228 14160 adb_trace.cpp:187] Installed as C:\Users\user\Desktop\platform-tools\adb.exe
adb D 08-15 22:11:43  6228 14160 adb_trace.cpp:187]
adb D 08-15 22:11:43  6228 14160 sysdeps_win32.cpp:402] adb_open: 'C:\Users\user\Downloads\lineage-18.1-20210812-nightly-fajita-signed.zip' => fd 2048
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:346] adb_connect: service: sideload-host:573814713:65536
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:155] _adb_connect: host:version
adb D 08-15 22:11:43  6228 14160 sysdeps_win32.cpp:846] port 5037 type tcp => fd 2049
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:107] writex: fd=2049 len=16 30303063686f73743a76657273696f6e 000chost:version
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=4
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=4 got=4 4f4b4159 OKAY
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:189] _adb_connect: return fd 2049
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=4
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=4 got=4 30303034 0004
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=4
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=4 got=4 30303239 0029
adb D 08-15 22:11:43  6228 14160 sysdeps_win32.cpp:537] adb_close: 2049(lo-client:5037)
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:155] _adb_connect: sideload-host:573814713:65536
adb D 08-15 22:11:43  6228 14160 sysdeps_win32.cpp:846] port 5037 type tcp => fd 2049
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:107] writex: fd=2049 len=18 30303065686f73743a74706f72743a61 000ehost:tport:a [truncated]
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:114] Switch transport in progress: host:tport:any
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=4
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=4 got=4 4f4b4159 OKAY
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=8
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=8 got=8 0100000000000000 ........
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:128] Switch transport success
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:107] writex: fd=2049 len=33 30303164736964656c6f61642d686f73 001dsideload-hos [truncated]
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=4
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=4 got=4 4641494c FAIL
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=4
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=4 got=4 30303036 0006
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=6
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=6 got=6 636c6f736564 closed
adb D 08-15 22:11:43  6228 14160 sysdeps_win32.cpp:537] adb_close: 2049(lo-client:5037)
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:360] _adb_connect error: closed
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:364] adb_connect: return fd -1
adb: sideload connection failed: closed
adb: trying pre-KitKat sideload method...
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:346] adb_connect: service: sideload:573814713
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:155] _adb_connect: sideload:573814713
adb D 08-15 22:11:43  6228 14160 sysdeps_win32.cpp:846] port 5037 type tcp => fd 2049
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:107] writex: fd=2049 len=18 30303065686f73743a74706f72743a61 000ehost:tport:a [truncated]
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:114] Switch transport in progress: host:tport:any
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=4
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=4 got=4 4f4b4159 OKAY
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=8
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=8 got=8 0100000000000000 ........
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:128] Switch transport success
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:107] writex: fd=2049 len=22 30303132736964656c6f61643a353733 0012sideload:573 [truncated]
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=4
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=4 got=4 4641494c FAIL
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=4
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=4 got=4 30303036 0006
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:81] readx: fd=2049 wanted=6
adb D 08-15 22:11:43  6228 14160 adb_io.cpp:97] readx: fd=2049 wanted=6 got=6 636c6f736564 closed
adb D 08-15 22:11:43  6228 14160 sysdeps_win32.cpp:537] adb_close: 2049(lo-client:5037)
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:360] _adb_connect error: closed
adb D 08-15 22:11:43  6228 14160 adb_client.cpp:364] adb_connect: return fd -1
adb: pre-KitKat sideload connection failed: closed
adb D 08-15 22:11:43  6228 14160 sysdeps_win32.cpp:537] adb_close: 2048(C:\Users\user\Downloads\li

I would assume that those symptoms are connected and I did something wrong with the linage installation, but since everything else (upgrades within 17.1, all apps etc.) I do not know where to look at. Any suggestions?

Edit:

Seems like I prematurely considered my phone to be the culprit, because of the custom setup. I did check it with another PC and file transfer works there without problem. Unfortunately, I cannot work with ADB there, but I will try to check my PC and iterate over the ADB-/Phone-Drivers.