The return of adverse weather prompted several teams to scramble for wet tires as the Total 24 Hours of Spa reached its six-hour mark.
SMP Racing Ferrari driver Mikhail Aleshin held the lead when the first quarter of racing ended, while Christian Engelhart was second in the No. 63 GRT Grasser Racing Lamborghini Huracan GT3 Evo.
They were ahead of the No. 88 AKKA-ASP Mercedes-AMG GT3 and the pole-sitting No. 4 Black Falcon Mercedes which has led large parts of the race so far.
A lengthy safety car period lasting 25 minutes was held during the fourth hour when Ryan Ratcliffe’s Team Parker Racing Bentley Continental GT3 made heavy contact with the outside tire wall at Stavelot.
R-Motorsport Aston Martin driver Matt Parry also had an off at the quick left-hand corner and was also forced to retire despite not triggering a race intervention.
Penalties have hindered some of the early lead contenders, including the Porsche 911 GT3 R entries from GPX Racing and the No. 998 ROWE Racing crew.
ROWE’s machine was leading near the end of the fourth hour with Nick Tandy at the wheel when it was called to serve a drive-through for improving on one of its best sector times under double yellow flags.
This was swiftly followed by a drive-through for the second-placed No. 563 Orange 1 FFF Racing Team Lamborghini, promoting the No. 1 WRT-entered Audi into the lead for a period.
The No. 1 Audi and the No. 4 Mercedes have been the primary cars sharing out the lead, although a clear pattern at the front has yet to emerge.
Early leader GPX Racing, meanwhile, was later handed a drive-through of its own for a pit stop violation.