B767 Captain reported unscheduled stab trim EICAS during take off resulting in a rejected takeoff. Flight returned to hard stand.

Narrative

FLT XXXX ZZZ-ZZZ1 Aircraft X. TOGW 435.3 F15. On takeoff roll RWY XXR after AUTO THROTTLE callout; FLT XXXX had an EICAS CAUTION UNSCHED STAB TRIM. A low-speed abort was accomplished at approximately 65kts. CAP let aircraft roll out to taxiway 1 to minimize braking impacts. AUTO BRAKES did not engage. Rejected takeoff checklist was accomplished and FLT XXXX was given taxi instructions to intersection 2 to troubleshoot. After accomplishing non-normal checklist FLTXXXX contacted Maintenance Control via SATCOM. Flight returned to hardstand for Maintenance attention. Extreme language barrier with local Maintenance. Maintenance/ Chief Pilot contacted for coordination. Some concern and frustration about repeated contact from Crew Desk about crew day extension when CAP primary concern was coordination of malfunction resolution; PAX communication/comfort and coordination with station Gate Agent from hardstand with no iPad connectivity and limited functioning cell phones. Crew worked problem for 3 hrs. Were then told they could retroactively extend crew day. Maintenance conditions were still unresolved.2 Tech OPS personnel were later flown in to attend to maintenance issue/sign off. Flight was cancelled and rescheduled as cargo section for following day. Follow up communication with Maintenance Control/Chief Pilot.