There is nothing wrong with the stamps but rather their postmarks. This is probably quite impossible to appreciate from the picture alone. I doubt that many collectors would be able to tell that the postmarks are actually forged without having the stamps at hand with some help from technology. The postmarks on the stamps are the Madame Joseph forged postmarks (Type 311) found on North Borneo stamps.
The postmarks are partly struck on the stamps and are in fact type 311 of Madame Joseph forged postmarks – JESSELTON single ring cds dated 15 JA 48.
The postmark resembles the first Australian post-war type and was applied using a high quality wood canceller. According to David Horry in Gibbons Stamp Monthly (June 2013, p.90), new evidence suggests that the wooden instruments were the work of master forger Raoul de Thuin and were made in Belize and Merida, Mexico from 1939-1949.
Forged Postmarks on North Borneo Stamps
According to Derek Worboys who has written a book entitled Madame Joseph Forged Postmarks which was published by the Royal Philatelic Society (RPSL), there are 5 forged North Borneo postmarks attributed to Madame Joseph. These are:
GPO 22 AUG 1911 (Type 307)
SANDAKAN 16 JAN 1916 (Type 308)
JESSELTON 22 AUG 1931 (Type 309)
JESSELTON 22 AUG 1941 (Type 310)
JESSELTON 15 JAN 1948 (Type 311)
Derek Worboys, a retired stamp dealer, purchased the Joseph instruments and paraphernalia from Clive Santo in the early 1990s to prevent their further use. The items were in the estate of Santo’s late father, George who died in 1990.
Madame Joseph was believed to the an active stamp dealer in London and had premises in Irving Street, just off Charing Cross Road. In conjunction with her collaborators, over 400 fake cancels were used dated up to 1949 mainly on British Commonwealth stamps.
Further reading: Madame Joseph forged postmark on Jesselton GPO 22 AUG 1911