Emerald Rom hack editing / black screen after elite 4

Hi guys,

this is my first post.

So I was editing an emerald rom to make my own rom hack.
I tested it to make notes what has to be changed or balanced.
After I beat the Elite 4 and Champion and the outro came, a black screen appeared which basically freezes the game.
Also resetting to title screen doesn't work anymore (neither in this situation nor when you play the game normally and everything is fine) - just another black or white screen appears

So my question is how can i fix that?
I can remember I also faced this problem when i beat the Platinum Renegade Champion after the outro.

To give you more information, this is everything I "edited" so far in this order:

- I changed the enemy teams in "Hopeless Trainer Editor"
- I changed the encounters in "Advance Map"
- Some minor map changes in "Advance Map"
- I changed some Items in "LSA Complete Item Editor"
- I changed trade evolutions in "PGE"
- I made TM's reusable by a minor change by scripting with "Gold Finger"
- I edited some scripts like weather, pokemart items etc with "Advance Map"

I made savefiles after every step just in case.

While testing the game i just found one single bug:
The Woman in Slateport City right next to the Energy Guru started at some point in the game to repeat the words from the last NPC I spoke to.
But I don't know if this can cause something.

If you need more information that you can help me just lmk.

Thank you in Advance!

Heiner291