Walking on Water with collisiongroups is half-malfunctioning

Okay, so I’m trying to create a walk-on-water serverscript using collisiongroups, as seen here:

local ps = game:GetService("PhysicsService")
local module =  require(game.ServerScriptService.Modules.jesusPeople) -- script for walk-on-water user IDs
local localplayer = "Character"
local water = "Water"
-- Create two collision groups
ps:CreateCollisionGroup(localplayer)
ps:CreateCollisionGroup(water)
ps:SetPartCollisionGroup(script.Parent, water)

local function setGroups(character)
	for _, child in ipairs(character:GetDescendants()) do
		if child:IsA("BasePart") then
			print("It's a basepart.")
			ps:SetPartCollisionGroup(child, localplayer)
			ps:CollisionGroupSetCollidable(localplayer, water, true)
		end
	end
end

local function onCharacterAdded(character)
	print("characterAdded")
	setGroups(character)
end

game.Players.PlayerAdded:Connect(function(player)
	for i, v in ipairs(module.gods) do
		print(v)
		if player.UserId == v then
			print("player's userid is equal to one of the IDs in the module.gods table")
			player.CharacterAdded:Connect(onCharacterAdded)
		end
	end
	print("playerAdded!")
end)

The modulescript it calls contains the following code:

local module = {
	gods = {
		25297190, -- me
		109844063, -- superstrongtitan
	}
}

return module

Pay close attention to

ps:CollisionGroupSetCollidable(localplayer, door, false)

In regards to the large, former block of code, there are no error outputs. In fact, everything prints nicely. It even works, but only half the time. In the line of code above ^^^, the code works. When I set the water to CanCollide and run this script, it allows me to fall through it, easy peasy.
The problem shows itself when I set it to Non-CanCollide and set

ps:CollisionGroupSetCollidable(localplayer, door, true)

to true instead of false.
Upon changing it, yes, there are no errors, and everything prints fine.

Does anyone know what’s going on here? I’ve never had an error like this before…

Please feel free to share your thoughts.