XRAY - Model racing cars

hi ,

my local track is an astroturf surface and is very bumpy , and has one BIG table top jump! , my car is fantastic over all the track ... exept the big jump. It seems to land very heavy and bottom out ?

and also through a 20 min final my car begins to loose some steering , is this the center or front diff oil getting hot ?

but the normal bumps i can ride very easily & quickly

setup = front , blue grey springs, 600cst oil std shock pistons
rear , grey springs , 300cst oil std shock pistons
front diff= std , center diff = std , rear diff = std

thanks in advance .!