Is waiting in adjudication for more than 3 years normal

If there are red flags on the background investigation, is it possible for a case to even go to adjudication? I had read a few posts that talked about Naturalized citizenship, foreign ties (supporting family overseas) etc. that play a role during adjudication - how does the adjudication work in such a scenario? I work with a lot of colleagues that are foreign born and have quite a bit of family ties that got through the process with no problem.