Walls disappearing help needed

Hi, I'm a new user who is trying to make his first game using DBpro.
When my charachter is inside a building the front wall disappears showing the backdrop while the right and the left one stay normally showed.

when I turn the charachter left the old front wall appears and the old left one disappears.
What I could do ?

If I'm not clear is because I'm Italian, I hope I have expressed my problem as clearly as possible.


that's my code


sync on
sync rate 60
backdrop on




rayman = 2
load object "terrain.x", 1
load object "palazzo.x", 5
load object "pedana.x", 6
load object "goku.x", rayman
load image "sunset.jpg", 1



gira = 0
count = 0

do
k = object position x (rayman)
j = object position z (rayman)
print "la tua x e' " , k
print "la tua z e' " , j

if object position x (rayman) < -45800 then stop object (rayman); move object (rayman), 20
if object position x (rayman) > 45800 then stop object (rayman); move object (rayman), 20
if object position z (rayman) < -45800 then stop object (rayman); move object (rayman), 20
if object position z (rayman) > 45800 then stop object (rayman); move object (rayman), 20


if upkey() = 0 then anim = 0
if upkey () = 1 then anim = 1

if downkey () = 1 then if gira = 0 then yrotate object rayman, object angle y (rayman) + 180 ; count = 0 ; gira = 1

rem animazione passi
select anim
case 0
set object frame rayman, 0
stop object rayman
endcase

case 1
if object playing (rayman) = 0 then play object rayman, 2,49
move object rayman, -20

endcase

case default
text 10,10,"error"
endcase
endselect
rem fine animazione passi

if rightkey () = 1 then yrotate object rayman, object angle y (rayman) + 2

if leftkey () = 1 then yrotate object rayman, object angle y (rayman) - 2


set camera to follow 0, object position x (rayman), object position y (rayman),object position z (rayman), object angle y (rayman) -180, 800, 800, 25,0




if count = 10 then gira = 0
count = count + 1



sync
loop