[General Accessories] marekyggdrasil:
I extracted some debug logs from `logcat`

01-16 17:34:50.364 26036 26036 D AndroidRuntime: Calling main entry com.android.commands.bu.Backup
01-16 17:34:50.366 26036 26036 D bu : Beginning: backup
01-16 17:34:50.361 26036 26036 W main : type=1400 audit(0.0:1262): avc: denied { ioctl } for path="socket:[284547]" dev="sockfs" ino=284547 ioctlcmd=7704 scontext=u:r:shell:s0 tcontext=u:r:adbd:s0 tclass=unix_stream_socket permissive=0
01-16 17:34:50.368 1633 3281 V BackupManagerService: Requesting full backup: apks=false obb=false shared=false all=false system=true pkgs=[Ljava.lang.String;@542d227
01-16 17:34:50.369 1633 3281 I BackupManagerService: Beginning full backup...
01-16 17:34:50.369 1633 3281 D BackupManagerService: Starting backup confirmation UI, token=2090823965
01-16 17:34:50.370 1633 3281 W ContextImpl: Calling a method in the system process without a qualified user: android.app.ContextImpl.startActivity:668 com.android.server.backup.BackupManagerService.startConfirmationUi:8877 com.android.server.backup.BackupManagerServiceInjector.startConfirmationUi:37 com.android.server.backup.BackupManagerService.fullBackup:8740 com.android.server.backup.Trampoline.fullBackup:230
01-16 17:34:50.370 1633 3281 W ContextImpl: Calling a method in the system process without a qualified user: android.app.ContextImpl.startActivity:680 android.app.ContextImpl.startActivity:669 com.android.server.backup.BackupManagerService.startConfirmationUi:8877 com.android.server.backup.BackupManagerServiceInjector.startConfirmationUi:37 com.android.server.backup.BackupManagerService.fullBackup:8740
01-16 17:34:50.373 1633 3281 I ActivityManager: START u0 {act=fullback flg=0x10000000 cmp=com.android.backupconfirm/.BackupRestoreConfirmation (has extras)} from uid 1000 on display 0
01-16 17:34:50.382 1633 1689 V BoostFramework: BoostFramework() : mPerf = com.qualcomm.qti.Performance@475df1f
01-16 17:34:50.383 1633 1689 V BoostFramework: BoostFramework() : mPerf = com.qualcomm.qti.Performance@125a26c
01-16 17:34:50.383 1633 3281 E ActivityManager: Invalid thumbnail dimensions: 0x0
01-16 17:34:50.404 1633 3708 I Timeline: Timeline: App_transition_ready time:6884550
01-16 17:34:50.405 1633 3281 D BackupManagerService: Waiting for full backup completion...
01-16 17:34:50.424 1633 1647 D CryptdConnector: SND -> {8 cryptfs cryptocomplete}
01-16 17:34:50.424 1633 2858 D CryptdConnector: RCV <- {200 8 1}
01-16 17:34:50.428 1633 1689 I Timeline: Timeline: App_transition_ready time:6884574
01-16 17:34:50.429 1633 1689 I Timeline: Timeline: App_transition_ready time:6884575
01-16 17:34:50.446 1633 1689 I Timeline: Timeline: App_transition_ready time:6884591
01-16 17:34:50.482 1633 1689 I ActivityManager: Displayed com.android.backupconfirm/.BackupRestoreConfirmation: +86ms
01-16 17:34:51.172 1633 1689 I Timeline: Timeline: Activity_windows_visible id: ActivityRecord{aa58cd4 u0 com.android.backupconfirm/.BackupRestoreConfirmation t1566} time:6885318
01-16 17:34:51.176 1633 1689 I Timeline: Timeline: App_transition_stopped time:6885322
01-16 17:34:51.442 1633 3822 D BackupManagerService: acknowledgeFullBackupOrRestore : token=2090823965 allow=true
01-16 17:34:51.448 1633 26062 I BackupManagerService: --- Performing full-dataset adb backup ---
01-16 17:34:51.449 1633 26062 W ContextImpl: Calling a method in the system process without a qualified user: android.app.ContextImpl.bindService:1295 com.android.server.backup.BackupManagerService$FullBackupObbConnection.establish:3164 com.android.server.backup.BackupManagerService$PerformAdbBackupTask.run:3818 java.lang.Thread.run:818 <bottom of call stack>
01-16 17:34:51.473 1633 26062 D CryptdConnector: SND -> {9 cryptfs cryptocomplete}
01-16 17:34:51.474 1633 2858 D CryptdConnector: RCV <- {200 9 1}
01-16 17:34:51.480 1633 3281 D BackupManagerService: Full backup processing complete.

I tried ADB versions `1.0.26`, `1.0.29`, `1.0.31`, `1.0.32`, `1.0.36`