As this is a Jinsan issue rather than any particular brand issue I wrote to both Eric and Sam as below and did not receive the courtesy of a reply.
I believe it's pretty unique however to the African skin tone.
Another vendor who is a friend reported to me similar experience with one of the Jinsan African skin tone dolls.
Best wishes
Harem
Dear Sam and Eric
I'm writing to you as the producers of the largest numbers of dolls as the majority of the Jinsan output.
Attached are some photos that I took today of an 18th month old Jinsan doll of which I know the origins as a genuine Jinsan doll and her intervening history.
The doll has been owned by a female art student who, obviously, has not used it for sexual purposes. Were this doll to have been owned by a male and used sexually and had the usual damage to private parts we'd blame it on the customer rather than the factory the temptation would be to blame the customer. But this doll has not been used and the student didn't have time to do photography with the doll that she expected to achieve during her degree course. So the doll stood in her room, and for the last nine months has been laying down stored at her parents' home.
Effectively without any use at all the TPE has fallen to pieces within 18 months.
With a soldering station I was able to heal cracks at the surface but when bent they opened up again.
The student is taking a year off and returning to do a Masters Degree in the psychology of photography the following year and in which she expected to be using her doll. In the event, it won't survive a year of non-use in the meantime.
The quality of this output of the Jinsan factory from December 2016 / January 2017 is unacceptable and of great concern and needs to be drawn to the attention of the factory management at the highest level.
Best wishes,