Flashtool hangs on dumping TA Partition

I have always been able to flash FTF files without issues, but today is not like that:

Code:

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23/023/2015 00:23:58 - INFO  - Selected Bundle for Sony Xperia Z3 Compact (D5803). FW release : 23.4.A.0.546. Customization : Customized NL
23/023/2015 00:23:58 - INFO  - Preparing files for flashing
23/023/2015 00:23:59 - INFO  - Please connect your device into flashmode.
23/024/2015 00:24:06 - INFO  - Device connected in flash mode
23/024/2015 00:24:06 - INFO  - Opening device for R/W
23/024/2015 00:24:06 - INFO  - Reading device information
23/024/2015 00:24:06 - INFO  - Phone ready for flashmode operations.
23/024/2015 00:24:06 - INFO  - Opening TA partition 2
23/024/2015 00:24:06 - INFO  - Current device : D5803 - YT910W1ZV8 - 1288-5414_R7C - 1285-6521_23.4.A.0.546 - GLOBAL-LTE_23.4.A.0.546
23/024/2015 00:24:06 - INFO  - Closing TA partition
23/024/2015 00:24:06 - INFO  - Start Flashing
23/024/2015 00:24:06 - INFO  - Processing loader.sin
23/024/2015 00:24:06 - INFO  -    Checking header
23/024/2015 00:24:06 - INFO  -    Flashing data
23/024/2015 00:24:08 - INFO  - Loader : S1_Root_9c84 - Version : MSM8974AB_27 / Boot version : S1_Boot_MSM8974AC_LA3.0_L_36 / Bootloader status : ROOTABLE
23/024/2015 00:24:08 - INFO  - Max packet size set to 512K
23/024/2015 00:24:08 - INFO  - Making a TA backup
23/024/2015 00:24:08 - INFO  - Opening TA partition 1
23/024/2015 00:24:08 - INFO  - Start Dumping TA partition 1
23/024/2015 00:24:24 - INFO  - Flash canceled

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I open the flash menu and then press cancel to stop the flash. The phone keeps working as normal, but I am unable to flash the FTF.
I am excluding system since I flashed my own-made pre-rooted FTF through TWRP.

Is there anybody familiar with this problem?