Thanks, got it. I've now found and made a C4 recovery file

So just to make sure I understand 100% before I start deleting stuff ... I just need to look for .img files that are dated in the last few days, and delete any/all of those? Any other files to delete?

There appears to be one in the Maps folder on the device dated March 2023 (which is probably the US map as it hasn't been updated for a long time due to limited internet) and one in the Maps folder on the SD dated 30 May 2025 ago, which is when I killed it.

I've copied everything off the unit's internal storage and off the SD (which reads fine installed in the Garmin) into a folder on my PC as a backup. The only file that won't copy is the IMG file dated 30 May 25 off the SD, which throws up an error saying "The value cannot be determined" just at the end of copying. I guess that means it's trashed.

My understanding is therefore, in sequence, I should:

Flash to C4 CURE firmware - done/successful
Find and delete IMG file causing the issue
Flash back to C4 standard firmware with Updater
Reboot device (I assume it will throw up an error saying no map)
Run Webupdater or Express to re-download map files

Is that correct? Thanks very much, making progress now and very pleased about that! It has a lifetime sub for the maps, so hopefully it will still recognise that.