Nearside seat/bed runner not fully extending

Could anyone point me in the right direction on this.
Someone came to view my van which is up for sale with MH Depot. The MH Depot chap had demonstrated the equipment including having already had the bed fully made up with both the offside sofa and nearside seat fully extended, but the buyer wanted to see the nearside seat extended again.
At this point the seat would not fully extend (this has never happened before), but the seat would not fully extend. The lock was definitely dis-engaged, but the seat comes to a "soft stop" about halfway extended. 
I think it is an issue with the sliding bracket closest to the sliding door as it seems to be out of synch in that the inner most rail of that bracket seems to be extending before it should.

Does anyone have any experience with these sliding brackets and can suggest what I can do to fix it>>>

Thanks
Andy

Check for screw head sticking out into the slide channel. We had that on Symphony.

Paulmold wrote:Check for screw head sticking out into the slide channel. We had that on Symphony.

Thanks, I will have a look.  Not sure that would be it as when I start to slide the seat after disengaging the lock the rail nearest the sliding door seems to extend before it should. It is difficult to explain but it is as if the rail extends before the actual seat.

I will take a closer look
Thanks

UPDATE......
After removing the seat to get a better view of the sliding rails I found a plastic end block missing from the suspect rail. 
I compared the movement of the suspect rail to the opposite one and deduced the inner rail needed to be forced backwards so it sat in the outer rail as per the good rail.
After pushing this in it then refused to travel in the opposite direction.
I placed a block of wood between the rear end of the rail and the wardrobe wall then pushed hard on the front end.
This forced the rail assembly back to how it should have been, and in the process the missing plastic end block popped out of the outer rail. I refit the end block and the rails are now working correctly.

Probably not explained this too well, but I understand what I mean. It was simply the arrangement of the three runners which make up the rail which had somehow managed to go out of synch with each other, probably caused by the potential buyer trying to force the seat back without disengaging the locking mechanism.