"* Be persistent in trying to get it to flash, it may take numerous attempts to flash a flaky device which moves in an out of preboot." if I am constantly in preboot mode even without button pressing how can the device move out of it.

Also it is unclear should I rename the firmware that is placed in the same folder as the updater.exe only 205001000960.rgn or 205001000960_cure.rgn? Using quickcure3.rgn do I need to rename it the same?

I tried a couple of times and I managed to get somewhere like 4-5 times. Once using an older version v2.7 (because I saw it was modified in 2012) but I got an error message "There is a problem with this GARMIN application...." than a couple of times with the v2.8 updater.exe and it asked me if I want to reinstall the same firmware version but when I clicked YES it went to a screen
"FENIX3 V9.60
Erasing...
(this may take a few minutes)" I left it there for more than an hour but nothing happened, progress bar did not move at all.

I was able to get to this point a few times but no progress after that and I have no idea why other times did not even manage to get here... it does not seem to be consistent.

In the meantime I read this post "How to unbrick a nüvi - step by step guide", and a couple of people had the same problem where they got the gps not responding error, in comment #70 you said "Connect a suitable USB cable directly to a REAR USB2 port of PC without a hub, don't use a front port or USB3 port" as I found out my laptop has only USB3 could this be why it can't get a connection?

When retrying the whole process should I turn off my device every time or is it not necessary because it is always in preboot mode?

Thanks for the quick reply (hope I can write thanks like this)