Town Reset?

DivinylsFan​  During a town reset, every sim and lot and object is MC-reset, the same way each one would be if you ran the MC reset commands individually.  Sims are sent to a safe place (home or off the map); objects in use, or stuck seemingly in use, are restored to default, although this doesn't always fix objects stuck in other ways; doors and staircases with existing issues may or may not be fixed; lots have all their objects reset, including any sims or animals that were present.

Additionally, it often happens that objects in sims' inventories are moved to the household inventory, which can be neutral or occasionally very problematic, as with career objects like the pager for cops and doctors.  But you can usually fix this by fiddling with DebugEnabler or just flushing the object and hoping the game provides a new one, which it typically will.

If you want your own sims not to be reset, you can exclude the active lot from town resets, under MC Settings.  Just make sure your sims are actually home.

A town reset is definitely not a last resort; in fact, many of us run one periodically just to catch any lingering issues that haven't made themselves known yet.  When I'm playing rotationally, I run one each time I switch households, typically every three sim-weeks, although that's a little more often than is necessary.  But there's no real harm in running them as often as you want, other than perhaps a bit of inconvenience.