One of the most irritating damages is a mutilated chain tensioner, usually found on a box store saw purchased by someone that knows nothing about chainsaws and never reads an owners manual. Owner hasn't paid attention to getting the tensioner tab fitted into the hole in the bar and has tightened down the bar nuts, squishing the tensioner. I have even found them with the threads stripped because the owner didn't realize the bar mount nuts had to be loose before using the tensioner. What hope is there if the simplest things can be an issue?