Trying checking your serial flash size. How much is the size of the serial flash, how much is already written in it and how much are you trying to add? This is usually a common reason for failure in writing.
I'm not quite sure where to look, to change this value.
I'm testing with the OTA_FR app and trying to update with the scan snip, just at the instructions are saying.
I have noticed that it is random how many blocks it gets to write, before it stops.
The OTA is mostly a platform operation, so we need to know a lot more about your platform, eg.
what is the MCU?
What is your serial flash size?
Did you get SPI to work already with serial flash?
What's the file size you are trying to copy?