[Android General] JuhaniJ:
Here are some additional logs about the situation. These logs are from the same case as the SP Flash Tool console output and dmesg from my previous posting.

Excerpt from file QT_FLASH_TOOL.log:

08/25/2019 21:10:57 FlashTool[1613][140269737375488][D]: SearchUSBPortPool(): USB port is obtained. path name(/dev/ttyACM0), port name(/dev/ttyACM0)(../../../flashtool/Conn/USBSetting.cpp,161)
08/25/2019 21:10:57 FlashTool[1613][140269737375488][D]: Search(): Scaning USB port succeeded!(../../../flashtool/Conn/USBSetting.cpp,139)
08/25/2019 21:10:57 FlashTool[1613][140269737375488][D]: PreConnect(): USB port detected: /dev/ttyACM0(../../../flashtool/Conn/ConnMedia.cpp,68)
08/25/2019 21:10:57 FlashTool[1613][140269737375488][D]: ConnectBROM(): BROM connected(../../../flashtool/Conn/Connection.cpp,80)
08/25/2019 21:10:57 FlashTool[1613][140269737375488][D]: ConnectDA(): Downloading & Connecting to DA...(../../../flashtool/Conn/Connection.cpp,111)
08/25/2019 21:10:57 FlashTool[1613][140269737375488][D]: ConnectDA(): connect DA end stage: 2, enable DRAM in 1st DA: 0(../../../flashtool/Conn/Connection.cpp,115)
08/25/2019 21:10:57 FlashTool[1613][140269737375488][D]: cb_com_init_stage(): COM port is open. Trying to sync with the target...(../../../flashtool/Arg/BootRomArg.cpp,183)
08/25/2019 21:10:57 FlashTool[1613][140269737375488][D]: cb_com_init_stage(): hCOM(0x7f93100041f0).(../../../flashtool/Arg/BootRomArg.cpp,186)
08/25/2019 21:10:57 FlashTool[1613][140269737375488][D]: ConnectDA(): Failed to Connect DA: S_BROM_DOWNLOAD_DA_FAIL(../../../flashtool/Conn/Connection.cpp,130)
08/25/2019 21:10:57 FlashTool[1613][140269737375488][D]: Disconnect(): Disconnect!(../../../flashtool/Conn/Connection.cpp,140)
08/25/2019 21:10:58 FlashTool[1613][140269737375488][D]: run(): BROM Exception! ( ERROR : S_BROM_DOWNLOAD_DA_FAIL (2004)

File BROM_DLL_V5.log:

08/25/19 21:10:57.809 BROM_DLL[1613][1654]: DEBUG: Boot_FlashTool(): Cable Type - UART (brom_mt6276.cpp:1307)
08/25/19 21:10:57.809 BROM_DLL[1613][1654]: DEBUG: Boot_FlashTool(): SV5 starts... (brom_mt6276.cpp:1310)
08/25/19 21:10:57.809 BROM_DLL[1613][1654]: DEBUG: Boot_FlashTool(): CALLBACK_COM_INIT_STAGE(0x00492E80).... (brom_mt6276.cpp:1321)
08/25/19 21:10:57.809 BROM_DLL[1613][1654]: DEBUG: BRom_GetBootLoaderVer(): enter ... (brom_base.cpp:1866)
08/25/19 21:10:57.811 BROM_DLL[1613][1654]: DEBUG: BRom_GetBootLoaderVer(): ver(0x01). (brom_base.cpp:1890)
08/25/19 21:10:57.811 BROM_DLL[1613][1654]: BRom_PowerKeyLockSentry(): execute m_base.SetReg_LockPowerKey(). (brom_base.cpp:2213)
08/25/19 21:10:57.811 BROM_DLL[1613][1654]: BRom_Base::BromCmd_GetSecConf(): enter ... (CSLA_SV5.cpp:412)
08/25/19 21:10:57.812 BROM_DLL[1613][1654]: DEBUG: Write8DataWithEcho(): =0, cmd(0xD8) (brom_base.cpp:1321)
08/25/19 21:10:57.812 BROM_DLL[1613][1654]: BRom_Base::BromCmd_GetSecConf(): OK. (CSLA_SV5.cpp:436)
08/25/19 21:10:57.812 BROM_DLL[1613][1654]: DEBUG: onDAWillBeDownloaded(): sec_config = 0x00000001 (boot loader) (secure_handle_brom.cpp:151)
08/25/19 21:10:57.812 BROM_DLL[1613][1654]: DEBUG: BRom_GetVer(): enter ... (brom_base.cpp:1747)
08/25/19 21:10:57.813 BROM_DLL[1613][1654]: WARN: BRom_GetVer(): BROM_SCMD_GET_BROM_VER(0xFF) is not support! (brom_base.cpp:1764)
08/25/19 21:10:57.813 BROM_DLL[1613][1654]: DEBUG: BRom_GetBootLoaderVer(): enter ... (brom_base.cpp:1866)
08/25/19 21:10:57.813 BROM_DLL[1613][1654]: DEBUG: BRom_GetBootLoaderVer(): ver(0x01). (brom_base.cpp:1890)
08/25/19 21:10:57.813 BROM_DLL[1613][1654]: DEBUG: SearchDA(): SearchDA [0] [6735 2601] [CA00 CA00 1] [0000 0000 1] (flashtool_handle_internal.cpp:5638)
08/25/19 21:10:57.813 BROM_DLL[1613][1654]: DEBUG: SearchDA(): SearchDA [1] [6735 6570] [CA00 CA00 1] [0000 0000 1] (flashtool_handle_internal.cpp:5638)
08/25/19 21:10:57.813 BROM_DLL[1613][1654]: DEBUG: SearchDA(): SearchDA [2] [6735 6571] [CA00 CA00 1] [0000 0000 1] (flashtool_handle_internal.cpp:5638)
08/25/19 21:10:57.813 BROM_DLL[1613][1654]: DEBUG: SearchDA(): SearchDA [3] [6735 6572] [CA00 CA00 1] [0000 0000 1] (flashtool_handle_internal.cpp:5638)
08/25/19 21:10:57.814 BROM_DLL[1613][1654]: DEBUG: SearchDA(): SearchDA [4] [6735 6580] [CA00 CA00 1] [0000 0000 1] (flashtool_handle_internal.cpp:5638)
08/25/19 21:10:57.814 BROM_DLL[1613][1654]: DEBUG: SearchDA(): SearchDA [5] [6735 6582] [CA00 CA00 1] [0000 0000 1] (flashtool_handle_internal.cpp:5638)
08/25/19 21:10:57.814 BROM_DLL[1613][1654]: DEBUG: SearchDA(): SearchDA [6] [6735 6592] [CA00 CA00 1] [0000 0000 1] (flashtool_handle_internal.cpp:5638)
08/25/19 21:10:57.814 BROM_DLL[1613][1654]: DEBUG: SearchDA(): SearchDA [7] [6735 6595] [CA00 CA00 1] [0000 0000 1] (flashtool_handle_internal.cpp:5638)
08/25/19 21:10:57.814 BROM_DLL[1613][1654]: DEBUG: SearchDA(): SearchDA [8] [6735 6735] [CA00 CA00 1] [0000 0000 1] (flashtool_handle_internal.cpp:5638)
08/25/19 21:10:57.816 BROM_DLL[1613][1654]: DEBUG: SearchDA(): DA_HANDLE(0x02936920):SearchDA(): DA[8] is selected! (flashtool_handle_internal.cpp:5660)
08/25/19 21:10:57.816 BROM_DLL[1613][1654]: DEBUG: CompareSingleKey(): DA entry key(67350). (da_entry_base.cpp:391)
08/25/19 21:10:57.816 BROM_DLL[1613][1654]: DEBUG: Boot_FlashTool(): (0x7f93100041f0): BRom_WriteBuf() ... (brom_mt6276.cpp:1478)
08/25/19 21:10:57.816 BROM_DLL[1613][1654]: BRom_MT6276::BRom_WriteBuf(): p_data_blocks(0x17DE6050). (brom_mt6276.cpp:957)
08/25/19 21:10:57.816 BROM_DLL[1613][1654]: BRom_MT6276::BRom_WriteBuf(): block_count(1), total_length(97120). (brom_mt6276.cpp:1003)
08/25/19 21:10:57.816 BROM_DLL[1613][1654]: com_base::getBaudRate(12): 19200 (com_base.cpp:340)
08/25/19 21:10:57.816 BROM_DLL[1613][1654]: com_util::GetCommPreference(0x7f93100041f0): baudRate(19200), packet_len(1024), accuracy(151). (com_util.cpp:247)
08/25/19 21:10:57.816 BROM_DLL[1613][1654]: BRom_MT6276::BRom_WriteBuf(): sending m_blocks[0]={ m_baseaddr(0x00200000), m_data(0x1CB26AE8), m_data_len(97120), m_data_sig_len(256) }. (brom_mt6276.cpp:1033)
08/25/19 21:10:57.819 BROM_DLL[1613][1654]: DEBUG: Write8DataWithEcho(): =0, cmd(0xD7) (brom_base.cpp:1321)
08/25/19 21:10:57.967 BROM_DLL[1613][1654]: ERROR: BRom_MT6276::BRom_WriteBuf(): Read16Data(): Status returns error (0x2001)! (brom_mt6276.cpp:1153)
08/25/19 21:10:57.967 BROM_DLL[1613][1654]: ~BRom_PowerKeyLockSentry(): execute m_base.SetReg_ReleasePowerKey(). (brom_base.cpp:2224)
08/25/19 21:10:57.967 BROM_DLL[1613][1654]: Boot_FlashTool(): DA_HANDLE->rwlock: READ_UNLOCK. (rwlock.cpp:339)
08/25/19 21:10:57.967 BROM_DLL[1613][1654]: ERROR: pre_download_da(): S_BROM_DOWNLOAD_DA_FAIL(2004),ft_handle(0x10005CC0): Boot_FlashTool(): fail! (flashtool_api.cpp:1565)
08/25/19 21:10:57.967 BROM_DLL[1613][1654]: pre_download_da(0x7f9310005cc0): DA_HANDLE->rwlock: READ_UNLOCK. (rwlock.cpp:339)
08/25/19 21:10:57.967 BROM_DLL[1613][1654]: ERROR: FlashTool_Connect_Download_InitDA(): FlashTool_Connect_Download_InitDA() fail, error S_BROM_DOWNLOAD_DA_FAIL(2004) (flashtool_api.cpp:1622)
08/25/19 21:10:57.968 BROM_DLL[1613][1654]: ERROR: FlashTool_Connect_Download_InitDA(): <ERR_CHECKPOINT>[150][error][2004]</ERR_CHECKPOINT> [S_BROM_DOWNLOAD_DA_FAIL] (flashtool_api.cpp:1624)
08/25/19 21:10:57.968 BROM_DLL[1613][1654]: ERROR: FlashTool_Connect_Download_DA(): S_BROM_DOWNLOAD_DA_FAIL(2004),ft_handle(0x10005CC0): FlashTool_Connect_Download_InitDA(): fail! (flashtool_api.cpp:1476)
08/25/19 21:10:57.968 BROM_DLL[1613][1654]: ERROR: FlashTool_Connect_Download_DA(): <ERR_CHECKPOINT>[149][error][2004]</ERR_CHECKPOINT> [S_BROM_DOWNLOAD_DA_FAIL] (flashtool_api.cpp:1478)
08/25/19 21:10:57.984 BROM_DLL[1613][1654]: FlashTool_Disconnect(0x10005CC0): mutex: LOCK ... (mutex.cpp:151)

Any ideas why Readback is failing?