I have seen some come into the shop both the Explorer and the Sovereigns where there is no rubber washer even on the rod and the bolts tightened until they were bent, the excuse was the coil was floppy so they tightened it even more. They lost the washers when they changed the coil and didn't think they needed them.
Now I have sold many Sovereigns, Explorers, some E-Tracs and a few Excalibur's and had 1 Sovereign XS2 with a bad sensitivity switch right out of the box, the first Explorers XS several had audio problems with the headphone jack and the plastic cracking which Minelab took care of. Had a new Excalibur that had a bad switch right out of the box and not a single E-Trac problem, so out of over 75 detectors I would say they do build good quality detectors. Had a Explorer XS get run over by a van and just had to get a new arm cuff and a lower rod which i had. Guy ask me to send his Explorer in as it didn't work, but it was just he blacked out the whole screen as he was trying to build a pattern without reading the instruction manual, so both of these were not Minelabs fault.
Critters Friend may have had a bad coil plastic, but chances are there was some misuse some where whether it was the coil bolt too tight, coil was hit with something or snagged on something and then twisted, but if he sends it in to Minelab and they find it was a defect they will give him a new coil as it is under warranty.
Percentage wise from what I sell Minelab has been the best percentage of less defect then my other ones i sell or used to sell, did have a Sovereign I bought used that didn't work when i got it and had to send it in, but was told someone had been in the box and messed around and shorted out lot of the circuit as it needed a whole control board as it was shot, but like I said before that wasn't Minelabs fault or defective.
I bet many of the problems we read about has to do with abuse or neglect on the Excalibur's.