Laminar Flamlet RANS to LES

LB

Hi, I am trying to model a large-scale non-premixed jet fire in FLUENT, I am using the laminar flamelet model. I am trying to use LES. The model runs fine with RANS. If I use my converged RANS as initial conditions for my LES within a few timesteps the flame dissapears. I have no idea what I am doing wrong. If I look at my fuel concentration at the jet inlet it drops from a mass fraction of 1 (RANS) to less than (0.4) LES in a matter of time steps. There seems to be nothing burning.

I've been trying to get to the bottom of the models in Fluent to see what changes with LES with limited sucess.

Please help!!