If this is in Game Maker Studio, move fall1 up in the resource tree so that it is above oPlayer. Then test your code. If this is GM8, it won't work that way.
So here's the thing we're trying to get at, which in similar situations is the root of the problem:
fall1 is a child of oParSolid. Inside fall1 is a collision event with oPlayer that should be telling fall1 to turn into object284 (your falling platform). Collisions are checked in the order of objects in the resource tree. So if oPlayer had a collision event with fall1 or a collision event with oParSolid, it would be run first and then you would (presumably) move oPlayer outside the collision. So then when it's ofall1's turn to run its collision event code, there is no longer a collision because oPlayer's collision event code already moved it out of the collision.
Update: Don't make fall1 a child of oParSolid. See if the code works that way. If it does, then it's oPlayer's collision with oParSolid getting run before fall1's that is causing the issue.