Player Character falls through static mesh w/ collision applied, won't snap to floor anymore

It’s there in the title, though these are two separate issues technically.

Have a static mesh for a tunnel that the player character will just fall through if placed there, which is a particular problem because it’s the starting area of the level. I know to apply collisions to the mesh and have. The problem remains and I have no idea why.

The other problem is something with the player character object itself. For whatever reason, the End key will no longer cause it to snap to floor from where I currently have it. Needless to say, manually lining the player character up each time I move it somewhere is not the most efficient use of my design time.

I have never had much luck actually getting replies on here to actually fix my problems and usually have to figure it out for myself, but if you have an idea how to fix either of these issues I implore you to help. Thanks if you do.

Was able to fix the snap to floor issue by rebuilding, though it won’t work in the tunnel area, in that case undoubtedly because of the same thing that makes the character fall through it. So really the collision failure issue with the tunnel is my problem.