I have a map built in WED with blocks roughly 64 quants cubed.

I allow grenades to be tossed forward from the player, these grenades hulls are roughly 8-9 quants in radius(set by min_x,max_x).

At certain angles the objects fall through floors and walls.
At slower speeds it happens less, but the speeds will be unrealistic if I slow them much more (toss a grenade at your feet).

Any pointers from you guys on how I could solve this issue?

I think it is because the speed of the movement is too high,so you just put this line in your main function " ph_fps_max_lock=210;
" the value may be higher

That worked, thanks a ton!