B767 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Time Pressure; Human-Machine Interface; Confusion; Troubleshooting
Aircraft Equipment Problem Critical; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Flight Crew Returned To Clearance
Aircraft
I was initially the PM (Pilot Monitoring) until approximately XA:50Z.  I was the first pilot to go into crew rest. The RF2 (Relief Pilot 2) and FO (First Officer) received the oceanic clearance at XA:58Z. There were no changes to the routing to the first oceanic waypoint and beyond in accordance with oceanic verification procedures. The following is the write up of the incident that occurred while I was in crew rest:Navigation error from FMS on ETOPS route. Crew verified oceanic routing in accordance with ETOPS procedures. Route was [...]. Crossing PIKIL in LNAV/VNAV; aircraft entered right turn as expected but turned past cleared route. PF selected heading select and returned to planned MAG HDG. Position report page showed passing 59n030w at the time we passed PIKIL with (coordinates X) next and (coordinates Y) after; (next +1). PIKIL was not depicted on the position report page. Coincidentally; PM had just accepted and executed flight level winds. Both FMSs showed same problem around PIKIL.After I came out of crew rest; the PM and PF (Pilot Flying) briefed me about the navigation incident. They had a properly programmed FMS with no modifications to the waypoints. The airplane behaved unexpectedly with a continual turn passing the first waypoint PIKIL and deviating from the magenta course line. They appropriately downgraded from the highest level of automation to correct the error. The RF2; who was the PM; captured the POS REPORT page when time allowed. The operating crew requested updated winds aloft around XC:00Z and were made available and executed around the time of PIKIL. Perhaps the new winds caused the FMS anomaly and shouldn't be requested anywhere near the first ocean entry point. This was stated as a known anomaly with the B767 FMS.
B767 Captain reported an internal aircraft issue which made the aircraft make a continual turn passing the first waypoint and deviating from the magenta course line.