My guess is because the first event is a parallel process, and it actually starts running again for one frame before the transfer happens. Since you set the player's opacity to 0 in that one frame, it is 0 once he is transferred to the new map.
If I am right about that, you can fix it just by putting an Erase Event command right after the transfer in the first event.
Also, sorry that it took so long. The normal forum for asking about eventing errors and the such is
Tutorials. Troubleshooting is for problems with the progam itself, about which I know nothing so don't often check.