Daniel Hope had his resin confisacted on leaving Shanghai earlier this month.
Cellist Trey Lee and another string player from Hong Kong suffered a similar experience on leaving the same airport. Every string player carries resin for bow maintenance.
The restrictions appear to be enforced at the moment only in Shanghai and Guangzhou. But under 2015 China rules resin is considered a potentially explosive substance. The advice is: do not carry resin in your hand luggage, until further notice.
Thanks to Rudolph Tang for the research.