In September, however, 23 American prisoners of war also refused repatriation, sparking a nationwide debate among journalists, politicians, military officials, psychiatrists, and the soldiers themselves. During a 90-day cooling off period, the GIs were held in the neutral zone at Panmunjom, but only two changed their minds in response to entreaties by U.S. officials and letters from the GIs’ families.

The commonly accepted reason at the time was that they were brainwashed while held prisoner. This was effectively confirmed by 149 other POWs held by the Chinese/North Koreans who “reported that their captors had waged a systematic effort to break down their beliefs and entice them to collaborate”

. . . .

Once in China the soldiers were sent to a collective farm to work. Within 1.5 years three of them ran away and sought refuge at the British Embassy in Peking. By 1958, 7 more of the soldiers had left China. By 1966, only two remained in China.

https://rarehistoricalphotos.com/american-soldiers-stayed-north-korea/