Honeywell gas valve shutting off

[PortMhor]

Type4600 valve shuts a minute or so after burners ignite. Have tested two thermocouples (existing one and a replacement) and getting 25 mV from each. Is there any additional diagnostic I should consider before sinking cash into new valve?

 

[PortMhor]

Update: polished the male and female contacts for the thermocouple/gas valve with wire wool, working fine now.