Fabian Schiller led the Lenovo Gulf 12 Hours with half of the race completed as the Pro entries gradually took over the overall top five.
The German racer, piloting the No. 14 Mercedes-AMG Team 2 Seas Mercedes-AMG GT3 Evo, held a lead of 14.527 seconds over the No. 46 Team WRT BMW M4 GT3 of Dries Vanthoor.
The Bahrain-flagged squad gained the lead of the race in the fifth hour of the contest as Maximilian Goetz completed a Turn 14 pass on the No. 21 Car Collection Motorsport Porsche 911 GT3 driven by Constantin Dressler.
Dressler himself had led since taking over from the No. 7 Herberth Motorsport Porsche of Daniel Allemann and remained there for several hours.
Meanwhile, the Pro cars, which were down the order after taking early mandatory timed 100-second pit stops, made their way through the field as the first half of the race unfolded.
The No. 14 Mercedes-AMG led the charge and first closed in on the Porsche, with Goetz rapidly closing down on Dressler and surpassing him with seven and a half hours remaining.
Blattner also dropped to third behind Vanthoor but remained in the Am-class lead, while Mikael Grenier took the No. 99 GruppeM Racing Mercedes-AMG into fourth place.
The mamba-liveried machine has completed the most mandatory stops of any of the Pro runners, but was delayed early on with a wheel issue during a pitstop.
However, Grenier made his way back onto the lead lap by passing Schiller at Turn 6 just before halfway, which saw the two cars make light contact.
Herberth’s No. 7 Porsche ran in fifth position, ahead of the No. 77 GruppeM Racing Mercedes-AMG currently in the hands of Frank Bird.
Bird held a lead of just over 30 seconds back to the No. 27 Optimum Motorsport McLaren 720S GT3 Evo of Rob Bell, which led the Pro-Am category.
Team WRT’s delayed second BMW ran in 19th place overall in the hands of Charles Weerts, six laps down after it spent 12 minutes in the pits with an exhaust issue earlier in the race.