Built a new firmware, flashes 'successfully' - But results in no changes.

[nimble99]

I have an IP camera based on DM368 board, and I have a firmware bin file which I have used to upgrade the camera.
I am now trying to enhance the firmware. I have used FMK to extract it, modify some files, and rebuild the bin file.
When I upload it to the camera, it says it was flashed successfully, reboots and everything is fine - but no files on the device have changed.

I am changing the html files to see if they are being applied, and they are not.
So, my thought, is that the firmware header file contains a version name (which it does appear to). Is it possible that the camera is seeing that the new firmware header has the same version as the installed one, and simply skips it?
If so, what's the safe way to modify the version number in the header IMG file - so that I don't break any checksums and brick the device?

Thanks!