Falcon 10 flight crew flying DA-10 aircraft reported thrust reverser failure on landing rollout.

Narrative

When approaching ZZZ from the Northwest I received the AWOS. This stated that the wind was variable from 040-290; 4 gusting 15 kt. I selected Runway XX to land. The landing attempt was successful but upon flare the wind shifted to a tailwind so some float occurred. Upon touchdown I advised the first officer to crack the thrust reversers. When they were both verified as deployed I applied power to the reversers. At about 60 percent N1 the right reverser closed as the left remained open under power. I called for the command to close both reversers. The inadequate training of the First Officer neglected that command. I had to single handedly emergency stow both reversers while maintaining center line to avoid mishap. The landing was without event other than terrified passengers. I write this today two fold. One: the reverser issue was brought up to and witnessed by chief pilot; manager; chief mechanic; [Person A] 3 times. Nothing was resolved. Nor communicated to the crew that the issue still remained. Two; I received a 300 Hour copilot that has never had any formal training for the type rated aircraft whatsoever; and the ensuing emergency caused undo chaos for such a simple remedy he was unable to accomplish. So my report is two fold. DA-10 thrust reversers closing after deployed. This particular organization employing unqualified pilots to meet their needs out of desperation at the cost of safety.