# Code doesn't run on micro:bit sometimes when copying hex file from Windows 10/11

**URL:** https://forum.makecode.com/t/code-doesnt-run-on-micro-bit-sometimes-when-copying-hex-file-from-windows-10-11/21744
**Category:** micro:bit
**Created:** [August 8, 2023, 4:49pm UTC](https://forum.makecode.com/t/code-doesnt-run-on-micro-bit-sometimes-when-copying-hex-file-from-windows-10-11/21744 "2023-08-08T16:49:43Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![kjw](https://avatars.discourse-cdn.com/v4/letter/k/e79b87/32.png) [@kjw](https://forum.makecode.com/u/kjw)
#### Post date: [August 8, 2023, 4:49pm UTC](https://forum.makecode.com/t/code-doesnt-run-on-micro-bit-sometimes-when-copying-hex-file-from-windows-10-11/21744/1 "2023-08-08T16:49:43Z")

</div>

I came across this last week. I was copying files to a BBC micro:bit V1 and it then stopped working. I found a `FAIL.TXT` file on the micro:bit drive with content of

> error: The hex file cannot be decoded. Checksum calculation failure occurred.  
> type: transient, user

It’s a bug which manifests in a few other ways and one that’s due to be fixed RSN apparently according to the description of it on [micro:bit Help & Support: Error transferring file to the micro:bit since Windows update in February 2023](https://support.microbit.org/support/solutions/articles/19000145576-error-transferring-file-to-the-micro-bit-since-windows-update-in-february-2023). WebUSB is unaffected, hence a decent workaround.

I thought I’d mention it here to raise awareness as it’s confusing when it works for a while then appears to stop working.