Link error when Trading (Pokemon)

[xDeuiii]

When I try to trade with myself with the same game (Pokemon Ruby), I get the "Link error" message everytime. What I did:
1st try:
File --> New Multiplayer Window
default settings
start trading as normal, tried trading Kadabra for Kadabra. Link error before Kadabra evolves

2nd try:
tried some settings I found on Youtube
Emulation --> Sync Video on, Sync audio off (I muted it personally cause the sound was annoying)
FPS target --> 30
"Pause when inactive" off
start trading as normal, tried trading Zigzagoon for Kadabra, Kadabra evolves successfully, but as soon as I try to walk out, Link error

3rd try:
Emulation --> Sync Video on, Sync audio off (I muted it personally cause the sound was annoying)
FPS target --> 15
"Pause when inactive" off
start trading as normal, gets Link error message in one of the emulation before even sitting down face to face

Using mGBA version 0.6.3. Using XBr lv3 shaders for all tries