Date: 201811
Local time of day: 1201-1800
Location: IAH.Airport, TX
Flight conditions: IMC
Weather elements / visibility: Rain
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Final Approach
Airspace: Class B IAH
ATC / advisory: TRACON I90
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Communication Breakdown; Confusion
Anomaly: ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control
When detected: In-flight
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: Upon landing in IAH we were advised by Ground Control to call IAH Approach Control for possible lateral deviation. This took us a complete surprise. We had been on the RNAV 26R Approach coming in from the west. As we approached SKLER we were cleared for the approach. Both myself and First Officer (FO) had verified the approach in the box; and FO fully briefed approach. As we approached DRKAR; Approach Control broke us off the approach and gave us a northerly heading. Controller stated aircraft in front of us did not make the turn in at DRKAR so he would vector us out for the ILS approach to Runway 26R. Neither myself nor the FO thought anything of it we just complied with ATC instructions. We continued and made a normal landing. Weather was heavy rain and low visibility but CAT 1 landing was successful by FO. On taxi in we were told to call Approach Control. I called immediately after we secured aircraft at the gate. The gentleman I spoke with had a very difficult time finding our flight and flight path in the computer. He stated that records show we turned in early at SKLER but no lateral deviation occurred and he took my personal information and said no further action required. He did say that they were getting many lateral deviations at that waypoint. Here is my huge concern; after all the attention we paid to setting up the box; briefing the approach and flying it with autopilot engaged; we could not understand how ATC could claim we had lateral deviation. Were we confused with another airplane in front of us? Did we load the box wrong? Or is there inherent problem with the waypoint that is loaded in the box on this approach? I do recall thinking that the display on the moving map looked like a 'fly by' at SKLER and not a 'Fly Over' waypoint as depicted in the JeppFD-Pro Chart. Or was it that because I was on lowest scale on map that made it appear so. This entire incident greatly concerns me. Usually when we make an error we can pinpoint it and make rational conclusions as to why it happened. This is truly not the case in this point. I for one will no longer accept an RNAV approach to this runway in the future until someone can explain what happened here. Please review this and have someone contact me with the resolution. As I said; ATC said two important things to me. That no lateral deviation actually occurred and that case was closed on their end.




Synopsis: B737 Captain reported the aircraft in front of them not flying a route correctly so ATC had to take their flight off the correct route to adjust for the prior flights problem.