https://support.garmin.com/en-GB/?faq=9G1aJHKuFmAr5AcXDyFS87&searchType=noProduct
(..)
I'm still offering to work with someone to get this fixed (as in fix the root cause for everyone going forward, not just get my particular installation working) if Garmin is interested.
I did screw up a little and not back up those old logs, but I'm pretty sure installing 6.6.0.0 again will break things again.