Fire Red Scripting Help Required

[raikoucolosseum]

Hello everyone!
Whilst I'm not new to PokeCommunity (I've been visiting the site and keeping up to date with everything here for so many years), this is the first time I've both contributed to a Thread, and attempted my own hack.
I've read as much as I can of tutorials and support threads on scripting, given it a go, and just can't seem to get it right.

I'm attempting to script Fire Red, and ultimately have fallen at the first hurdle. I want a script to begin as soon as the player steps downstairs. The script I've written is below, and you can probably understand what I'm trying to do here. Basically, every time I step downstairs into the room with MOM, the screen either goes black -or- nothing happens, and when I click on MOM, she moves and then the game crashes fatally.
PLEASE could someone help and educate me as I'm struggling to understand where I'm going wrong.
PS I have amended the script and item to something random as not to give away too much behind how the story actually begins.

Script here:

#dynamic 0x800000

#org @Start
lockall
checkflag 0x828
if 0x1 releaseall
setflag 0x828

applymovement 0x1 @mom_move
waitmovement 0x1
applymovement 0xFF @player_face
waitmovement 0xFF

msgbox @mom_speak MSG_KEEPOPEN
giveitem 0x1 0x1
msgbox @mom_speak2 MSG_KEEPOPEN

applymovement 0x1 @mom_return
waitmovement 0x1
releaseall
end

#org @mom_move
#raw 0x10 0x10 0x30 0xFE

#org @player_face
#raw 0x2F 0xFE

#org @mom_return
#raw 0x11 0x11 0x12 0xFE

#org @mom_speak
= Hi, dear!\nHappy Birthday!\pI hope you have a great time today.\nHere, take this masterball!

#org @mom_speak2
= Enjoy your special day!