Common movements can be an advantage
When the movement is a widely available quartz or mechanical caliber, repair or replacement can be straightforward.
Exterior parts may be the harder problem
Cases, proprietary crystals, crowns and bracelets can be more difficult to source than the movement itself.
Traditional Fossil watches and smartwatches are different
Connected Fossil smartwatches use a different type of electronics than conventional quartz and mechanical watches.
Mail-in is useful for more involved work
For Fossil watches that need more than a battery, movement, crystal and crown work are common reasons to send the watch in.