Box collision not triggering correctly?

Hi everyone
I am creating a vehicle game for multyplayer. When I respawn a player sometimes the respawn doesn’t work correctly and the player is respawned a the world origin with no pawn. To prevent this I have created a playerStart with a boxvolume that sets a boolean (isFree) when something is overlapping. This should set isFree to true if an other player is bloking this spawn.
When I am spawning the player I get all playerStarts and check if IsFree is true, then I get the location of the PlayerStart and respawn the player, if not I check the next playerSpawn.
Unfortunately the player still gets respawned in an occupied spawn.

Now I am debugging my spawns by adding a mesh to the spawnBP and toggle the visibility on actor begin/ end overlap.
It seems that the overlaps are only triggered when my collisionvolumes of my car enter the volume, my sceletalMesh is ignored.
I have four collisionvolumes on my car which are located at the four corners of the car.
Here are some pictures of my setup (can’t show the real car model, so I took the sedan)

I have tried different collision settings on the Spawnbox but this didn’t work.
Now i am rnning out of ideas…
Hope someone out there can help me