From a thread on .com, where exactly the same issue was raised…
Maybe open a case and citing the same as that seller ask SS to change the “SIOC” setting to false
Hello from Amazon Selling Partner Support,
From your email, I understand that are concerned about the ASIN: B01N911HME that is being sent in the own container.
Upon checking, I see that the shipping setting for ASIN B01N911HME is set to ship in own container. As per the process, the ASIN snickering will be done as per Ships in own container.
Please know in an effort to improve fulfillment processes and improve the overall Customer Experience, Amazon regularly reviews inventory to provide a better customer experience. An ASIN is deemed SIOC (Ships in own container) when it passes both a visual and physical evaluation. All single shipments will then not require an Amazon overbox.
The ASINs are monitored by the Customer Packaging Experience Team and if damage rates or negative packaging feedback increase because of the SIOC recommendation, Customer Packaging Experience Team will remove the certification.
Have a nice day.