Toyota has revealed that damage to the #7 car's aerodynamic profile led to a drop in pace for Kamui Kobayashi, Jose Maria Lopez and Mike Conway at the 6 Hours of the Nurburgring.
After leading the first two hours, the pole-sitting TS050 Hybrid lost around 20 seconds to the pair of Porsche 919s during the double-stints.
That gap multiplied over the remaining four hours, with the Toyota crew finishing third and over a minute behind the winning #2 Porsche of Timo Bernhard, Brendon Hartley and Earl Bamber.
The sister Toyota finished five laps down following a fuel pump malfunction on the formation lap, on a weekend that saw Porsche extend its World Endurance Championship points lead in both the drivers' and manufacturers' stakes.
After a post-race evaluation, the Toyota team found that the #7 car had suffered from an issue with "aerodynamic balance migration."
A statement issued by the team confirmed that the upset in balance was caused by damage to the underfloor of the TS050.
"Post-race investigation has revealed significant damage to the underfloor of the #7 car as well as a hole in the rear wing, which caused cracks in the main plane during the race," it said.
"The team believes this damage was caused by kerb riding for the underfloor and by unidentified flying debris which struck the leading edge of the rear wing main plane."
Kobayashi, Lopez and Conway left the Nurburgring fifth in the WEC drivers' championship, 71.5 points off the Bernhard/Hartley/Bamber Porsche crew.
The sister Toyota, driven by Sebastien Buemi, Anthony Davidson and Kazuki Nakajima, sits second in the table and 30 points adrift following its recovery drive to fourth place on Sunday.
