Custom Character falling through floor

When I spawn in the game next to the character,he looks normal and acts normal as well.But after some time of not interacting with the character,he will seem to fall down.
Once you approach the character he does follow you.


The entire character has cancollide off except for the HumanoidRootPart and Head.And everything except for those two have Massless on as well.

EDIT: I found out why he keeps falling,and it’s because after some time he will (Trip?) and enter FallingDown State.A quick fix is to disable that HumanoidStateType but I want to know exactly why,as he does still move quite a bit from his original spawnpoint.