It seems the [up_vnROM.net]_Oppo_F1s_(A1601)_MT6755_v5.1 flashing ROM I was using is missing files found in the [up_vnROM.net[_A1601EX_11_A.19_161011_MT6750_DLTOOL ROM used in the video.
I no longer get the FAIL: Add handle to list fail messages when I place DownloadTool_1612.8.exe in the [up_vnROM.net[_A1601EX_11_A.19_161011_MT6750_DLTOOL ROM directory.
Now I get a new error message.
The phone is detected and the red status bar goes to 100% in the first second or two of connecting the phone when flashing the recovery image but then sits for about 1 minute before an error pop up window appears.
I tried flashing the OPPO_F1S_mt6750_CTR_v5.7_Modified_product_device_prop.img recovery image three different ways to test whether using the [up_vnROM.net[_A1601EX_11_A.19_161011_MT6750_DLTOOL ROM, another of the MT6750 flashing ROMs, or one of the MT6755 flashing ROMs made a difference.
I got the same "error: Status_EXT_RAM_EXCEPTION(-1073414139)" message in all 3 scenarios:
Scenario 1:
[up_vnROM.net[_A1601EX_11_A.19_161011_MT6750_DLTOOL ROM directory given shorter name and containing the following additional files:
DownloadTool_1612.8.exe
OPPO_F1S_mt6750_CTR_v5.7_Modified_product_device_prop.img
Scenario 2:
[up_vnROM.net[_A1601EX_11_A.19_161011_MT6750_DLTOOL ROM directory contents overwritten by [up_vnROM]_A1601EX_11_A.15_160913_MT6750 contents and then directory given shorter name.
Then the following files copied into the [up_vnROM.net[_A1601EX_11_A.19_161011_MT6750_DLTOOL directory
DownloadTool_1612.8.exe
OPPO_F1S_mt6750_CTR_v5.7_Modified_product_device_prop.img
Scenario 3:
[up_vnROM.net[_A1601EX_11_A.19_161011_MT6750_DLTOOL ROM directory contents overwritten by [up_vnROM.net]_Oppo_F1s_(A1601)_MT6755_v5.1 contents and then directory given shorter name.
Then the following files copied into the [up_vnROM.net[_A1601EX_11_A.19_161011_MT6750_DLTOOL directory:
DownloadTool_1612.8.exe
OPPO_F1S_mt6750_CTR_v5.7_Modified_product_device_prop.img
If you could give me an idea where I am going wrong and things I could try, that would be really appreciated.