Same. I follow quarantine protocols by the book. My DT has UV running correctly 24/7.I'm in the ich magnet club with PBT's. That fish shot me in the foot after trying multiple QT attempts with them. I single handedly run both tanks @ ich management now (due to them) and livestock aren't dropping dead as some say they will.
If you've been doing this long enough many of us plopped and prayed for years and did (do) just fine, it's all about sourcing livestock from a relatively good source in the first place anymore.
My quarantine room is more elaborate than most people's display tanks.
They are just time bombs.
Not saying they can't be kept at all but I'm guessing extreme luck on top of perfect equipment, maintenance, protocols and food is required. With the luck component of sourcing the right fish being essential. I've seen them going from extremely happy and healthy to near death without any changes or external influences in a matter of a week.