It’s not uncommon for chinese engineered products to envolve rapidly (specially compares to ‘western’ engineering speed). Often they don’t even change the model number or outside look while improving the electrical design (from a manufacture point of view that could also be cost cutting measurements).
Also people should might take into account that 1, 10 or even 100 incidents doesn’t say much about quality or safety of a product that is sold million times.
As said before, I own plenty of sonoff as well as Shelly’s - only the later ones had a (luckily non fire) failure.
And when searching for the term “shelly fire” the latest result I get is only 4 hours old
https://m.facebook.com/groups/ShellyIoTCommunitySupport/permalink/6605961342836507/