Both companies have had SUVs stopped at the port.
Trade tensions with China have been heating up in the past several months, causing issues for imported cars entering China. We have already seen Ford experience holdups at the Chinese port and now both BMW and Mercedes have experienced issues, according to Automotive News. All of the SUVs that were held at port were built in the US either at Mercedes' plant in Tuscaloosa, Alabama or BMW's plant in Spartanburg, South Carolina, which may partially explain the holdup.
Reports indicate that Mercedes GLS and GLE models built in the US between May 4 and June 12, 2018, may have a "safety risk," according to a Chinese customs document. Authorities in Shanghai claimed that the rear brakes on the cars were "insufficient." BMW similarly had to hold cars at the Chinese port, though this issue was in regards to a recall of approximately 19,000 X3 and X4 vehicles. The recall affects vehicles built between mid-April to the end of June and was triggered by faulty brakes from a supplier.
Both BMW and Mercedes are working to rectify the respective issues so the SUVs can be sold in China. These may be minor issues, but with the current trade tension between the US and China, little issues like these may be more highly scrutinized when the cars in question were built in the US.