Sometimes there is a small % of uncatchable animals. Most will fall in the 80% and can be caught, and even most of the 20% can be caught with effort or even a lot of effort, but there are some that just are not going to be caught. Most of the time, these can't catch ums. for me, take off when the pressure is being applied. only to come back at a later time. I have had 2 beaver jobs come to mind that this happened and many coon, squirrel and groundhog jobs over the past 39 years that just takes off, and the person not looking for it can miss it. I am always looking for it, I have developed ways to see this. (6 phases of the grey squirrel, 6 phases of the coon and skunk phases) I know I am not the best, and may not catch all and everything all the time. sometimes the critter kicks my butt LOL Seeing it coming makes me feel better LOL
I remember a job where I was getting my tail handed to me by a groundhog. Every time I set up snare or cage it took off, (can't use killers or foot holds) I would pull the traps and 5 to 7 days the hog would come back. It was getting old LOL I was standing in the yard trying to think what I can do when this person comes to the fence and said I will show you how to catch that thing!!!!! I was in a very bad mood and Jeff you know how straight forward I can be when I am not happy. LOL I looked at him and said yeah think so????? He said watermelon you have to understand what your doing and know the right bait. I looked at him and said why don't you follow me to my truck I want to show you something. We went to my truck and there was bunch of critters in there. He looked for a sec, then looked at me with this dumb expression of wow. I said I think I know what I am doing now leave me alone!!!!!!! LOL I never got that hog It just got tired of me hounding it and disappeared.
A job like you talked about can happen, and to the person that is involved they may be causing the job to go that way, and not know it. I know I have caused it to happen. In their minds it is unsolvable. They think I am good so there for no one can do it. I call this thinking more highly of my self than I really am LOL And GOD brings a dumb animal I can't catch, to me to force me back to reality LOL
Maybe habitat modification is needed after they are taken out, to keep them out to really totally solve the problem long term, But folks tend to do what they want rather than what is smart for no other reason than this is what I think, based on nothing more than what I think. (that is a mind twister !!!!!) I can't tell you how many folks mess things up because they try modification while they are trying to catch. LOL A calm animal is easier to catch than a keyed up animal and habitat modification to make the animal leave or not want to be there will definitely key up a critter LOL