A common cause of large scale disorder is the presence of large stateless populations. The UN estimates that there are currently over ten million such people. Most of the stateless are that way because they don’t want to live where they, or their ancestors, came from. Thus there are a million Moslems in Burma who originally (often over a century ago) came from Bangladesh but don’t want to return there. They prefer to live in Burma, where most of the population is Buddhist. There is a similar situation in the African country of Ivory Coast, where 700,000 people (a quarter of the population) are migrants (or the descendants of migrants) from Burkina Faso, Mali and Ghana. Over the last half century Ivory Coast encouraged these people to come work on coffee and cotton plantations. Unfortunately Ivory Coast never agreed to offer citizenship and that led to a recent civil war between the migrants and the natives.
In the Middle East you have over 100,000 stateless nomads in Kuwait. Called the bedoon, these people were not considered Kuwaitis in 1962 (when Kuwait became independent) because the nomads came and went as they pleased and did not seem interested. But as the oil wealth grew interest arose. At that point Kuwait decided it was not making anyone else citizens. In Syria and Iraq there have been government attempts to punish rebellious Kurds by declaring some of them not citizens. That has not worked out well.
In Russia and former (after 1991) states of the Soviet Union there are over half a million people who ended up in a country that did not want them. About half of these “unwanted” are ethnic Russians who ended up outside Russia and liked being where they were but the locals did not want them. The other half were non-Russians who ended up in Russia but were not wanted. In Thailand there are over half a million tribal refugees from the numerous tribal rebellions in neighboring Burma. These people do not want to go back, would like to become Thai citizens but the Thais don’t want them.
In the Dominican Republic you have hostility towards migrants from neighboring Haiti which led to new laws making many migrants non-citizens. In Europe you have over 50,000 Roma (gypsies) who are nomadic and prefer to not register births with the state and not leave a paper trail. Many Roma have settled down, but enough have not to remain a problem.
There is a worldwide problem with illegal migrants going somewhere to find jobs, staying, not being detected for a while, if at all, and eventually their descendants demand citizenship. This often leads to violence and resists lots of solutions thus becoming long-term problems.