Write failed for OTA

Just started to play with updating OTA on an ESP8266, and have got everything working, but failing at the last hurdle. Iā€™m using the standard Blynk.edgent / Edgent_8266 sketch, can get Blynk.air and the device talking, and when I create a new shipping for an updated sketch (just incrementing BLYNK_FIRMWARE_VERSION), the 8266 connects and starts to download the new f/w. Then this is the output of the debug monitor:

[8836] Flashing...

 10%
 20%
 30%
 40%
 50%
 60%
 70%
 80%
 90%
ERROR[0]: No Error
[34701] Write failed. Written 468336 / 469008 bytes

 ets Jan  8 2013,rst cause:2, boot mode:(3,6)

load 0x4010f000, len 3460, room 16 
tail 4
chksum 0xcc
load 0x3fff20b8, len 40, room 4 
tail 4
chksum 0xc9
csum 0xc9
v00072750
~ld
[392] 

The Written number (468336 in the above example) is sometimes lower, sometimes higher, but the device always seems to crash out. By default, this will happen 3 times in 24hours before it does it all again.

What am I missing here? I have the right device selected in the Arduino IDE, I have the right device selected in the sketch (and have tried with a Node MCU with the same result). The device will happily flash via USB, just not OTA.

What does the Blynk.Air log say?

Pete.

Thanks Pete. Where can I find the log?

Console, Blynk.Air, shipment, Actions

Pete.

Not a lot of detail to go on:

STARTED
REQUEST_SENT
FIRMWARE_REQUESTED
FIRMWARE_UPLOADED
REQUEST_SENT
FIRMWARE_REQUESTED
FIRMWARE_UPLOADED
REQUEST_SENT
FIRMWARE_REQUESTED
FIRMWARE_UPLOADED
DOWNLOAD_LIMIT_REACHED