Let's post all logs in this thread.

C902 Flashing Logs:

4SE - tool 1.8.1
Selected model: C902
Selected operation: Flash
Selected interface: USB (BOOTROM)
Checking USB driver status...OK (SEMC Flash Device v2.2.0.5 | 5-4-2010)
Remove battery, wait a few seconds and insert it back
Plug USB cable holding both "2" and "5" buttons
Connected to USB4
You can now release the keys and allow the process to run. Do not disconnect the phone
Device identification...OK
Sending Preloader...OK
Sending IDloader...OK
ChipB3150 Model:C902 IMEI:35362603-791853-4 CID:52 Domain:RED
Uploading logic DB3150:
Detecting flash type...OK
ID: 2CAA (Micron)
Chip: Micron 2048 Mbit NAND (large page) x08
Logical address: 0x80000000
Size: 264 Mb
Reading TA security data...OK
Sending CSLoader...OK
C902 CID52 RedBrownBlue (R3EG004AS | 1208-6209) CUSTOMIZED UK/SWIFT BLACK
Flashing 276661140_0124A5A35FF0.SOFTWARE (816 blocks)...OK
Flashing 276728364_0124A5986370.SOFTWARE (704 blocks)...OK
Starting filesystem service...OK
Uploading 276184620_012475E0F700.FILE_SET (16 files)...OK
Shutting down device...OK
Operation completed successfully. You can disconnect the phone now
FINISHED [309sec]
... more to come!!