♤|SODA|♤ Interesting bug, good find!
In that case, one possible workaround fix for now would be to add a bit of script to both your tiles, just before the load_map() bit.
Try adding a stop_player() command first.
stop_player();
load_map("FM_map", coord[0, 0, 0]);
If its coming from a GM map that causes it, then hopefully, stop_player() being a GM function, should help.
It will force the player to stop on that tile and not continue moving.
May not work if the walk key is being held down...but give it a try and see if it helps.
Just a thought!
Another way, if stop_player() doesnt work is to use put_player(self); instead of stop_player on the load_map().
Even if the walk key is held down, put_player will force them to stop as part of putting them.
Might need to temporarily lock_player_movement(true) just before the put_player command though, and re-enabled it just after the load_map()