IMO,It may be a psych problem. These are often less experienced linesmen, with not many matches in top international football. Its not easy to them to judge, while the whole world watches him and the thought" dont make a mistake" dominate. They get nervous and If they are not sure, (it could be offside..) they raise the flaggs more or less automatically. They shouldn't do. So long the FIFA does not change the selecting system ,such problems will remain.