According to a South China Morning Post article, Hong Kong Customs officials investigated and ultimately raided a cell phone repair shop after receiving complaints from a trademark holder (not specified whether Apple or Samsung complained).
The article claimed the repair shop refurbished devices for clients in the US, UK and Australia that sent second-hand phones for repair at 1/3 the typical rate of an authorized repair facility. The repairs typically included replacing the screen or housing.
HK Customs officials claimed the repair shop used counterfeit parts to repair damaged iPhones, and seized over $120,000 worth of fake goods.
Based on the article, I’m pretty sure Apple complained about the IP violations since most Samsung phones do not have the housing replaced when being refurbished. While not listed in the article, the IP violations probably were for the wordmark “iPhone” or the trademark Apple logo found on the back housing. The iPhone replacement glass do not have any IP marks, so the seized goods were most likely the housings.