Royal Mail ref RY086841288GB. Been stuck at Guangzhou customs since 22.11.19. These are a return item because they are faulty. What is happening with my parcel??

Hi there, I returned an item to a company in China by Royal Mail (tracking code: RY440702334GB). It has been stuck at customs since 4th March 2023. Can you investigate why this item is still at customs?

I would like to ask for your help that the item I sent was originally intended for delivery to Macau S.A.R (Postal box 1089). However, I have been tracking the item for a long time, finally I found the item has been stuck in Ningbo's customs for 20 days. Subsequently, it was sent back to Shanghai customs. As of the latest update on 13-Feb, the item is shown as "sent to carrier." Can you please advise me on the status of the letter?
Actually, I have checked with Royal Mail multiple times, and they have informed me that the item is no longer in their care. The latest update on Royal Mail's tracking platform is from 4-Feb, but this status does not match the information provided by China Post. I am unsure of the current location of my item and would greatly appreciate your assistance in resolving this matter. Can you please help me to clarify where my item is located?
Please note that the item is a letter with dimensions of 22.9cm x 16.2cm and not a parcel. Thank you for your assistance.