Mine has been resetting since day 1. I had over 100 Hours on the 172, it now says 2.5 hours despite having all the time still showing in the log book.
I reported it via Zendesk a few months ago.
Since then I have mainly been flying the Caravan for over 200 hours, last update reset it back to zero again .
I have no mods at all unless you count a few orbx scenery addons purchased through the marketplace.
Think it’s just a bug.