Maybe the incident was caused by the crew failing to follow the RET centreline when vacating the runway and instead hugging the Northern edge on the RET only to encounter the notch in the RET where concrete suddenly becomes grass.
The notch is clearly visible on the AIP plates and Google Earth.
If this were the case it is similar to the incident to a Gulfstream at Biggin Hill in 2014 which commenced its takeoff run on 03 from the edge of the paved surface and then ran into the grass.
Just don’t tell Greta Thunberg it only had one Transatlantic passenger!