They noted that under Xi there was an increasing campaign of nationalism and the CCP increasingly began publicly blaming foreigners for any of Chinas internal woes. Furthermore the CCP has made the CCP, Chinese national identity and the Han ethnicity inseparable, so you cannot criticize one without offense to the other.
The CCP now actively promotes the Han ethnicity as the superior ethnicity and other minority groups try to make themselves "more Han" as they feel inferior for not being Han. The opposite of the West where every little group wants it's special identity.
Increasingly they were not allowed to enter some business such as restaurants as the owners outright didn't allow foreigners to enter anymore.
Black people in China especially are told to wait outside of certain establishments whilst their white friends can go in. Because one of the guys is South African, there is increased scrutiny of him as people assume he will be black. At one point he was outright lynched.
Eventually they started getting followed and denied access to parts of China as their reporting became less favorable, then outright banned from various provinces. They got into trouble for flying a drone in a public area and the authorities started outright harassing them. Eventually they had to skip into Hong Kong for refuge...but then Hong Kong was no longer safe either and then skipped over to Taiwan.
When leaving they were stopped and questioned and asked if they were returning...they wanted them to return as they most likely had intentions of detaining them in the future.