Very happy early Prusa Mini owner. I do remember some difficulty when assembling it, which lead to non-square axes. After an hour or so I eventually got right, so you might want to try redoing the tower assembly.
I don't have a filament sensor (I also print mainly small parts, so rare to hit the end of a spool), and haven't had any problems with heating elements, z steppers or nozzle crashes. I did experience the extruder clicking due to shrinking PTFE in the hot end, but I've ordered the E3D Revo mini hot end which will prevent that problem ever happening again.
I had clogging problems on mine - three or four different fixes to sort it out, and the thing that finally nailed it was replacing the PTFE hotend lining with Capricorn. It's been fire-and-forget since then.
I don't have a filament sensor (I also print mainly small parts, so rare to hit the end of a spool), and haven't had any problems with heating elements, z steppers or nozzle crashes. I did experience the extruder clicking due to shrinking PTFE in the hot end, but I've ordered the E3D Revo mini hot end which will prevent that problem ever happening again.