First, Which combineIJ If it is the Rotaries then have you had the rock door drop several timesIJ If so then you need to be opening the bottom screen and letting the trash out each time so that it doesn't pile up on each rock door reset.
I'm thinking you are the Joey with the R72. Check just under and to the rear of rock door. There is a easily removeable tin filler piece there that may of got bent rear ward. Something getting ejected from rock door can bend this filler back toward concave which will allow material from distribution auger and accelerator roll area to sneak by and get down into fan inlet area. Good luck.
Dan is probably right with bent filler plate.Also check under front drum of rear raddle.Floor can wear through.Would need to remove feeder housing and fabricate a plate similar to stainless wear plate under front raddle drum.
That plate is welded in but replaceable. I think it is reasonable priced. We don't remove feeder housing. We cut it out of there and then weld the new one in. Don't miss the reinforcement plate under floor for it doesn't come with new floor. A few years back the iron was changed to a high wear steel which should last longer. We have changed a couple in R50 and one in a R62. Them machines had did mega amounts of dirty edible beans and corn. I did hear of a guy who put a fabricated floor in without the dip in it and he said it helped prevent feeder pluging.