What difficulties do some missionaries face in their work?

Another answer from our community:

• There are many accounts of the persecution of Christians in China, and many Chinese Christians find it necessary to worship in secret. Many of these groups are non-denominational, but also come from a wide cross section of denominations and can suffer severely if detected. Foreign missionaries may not distribute literature, or preach to Chinese people outside of the government regulated churches in the Catholic Patriotic Association and Three-Self Patriotic Movement.