What does, "DataModel was not available" mean when using Humanoid:ApplyDescription?

Hi, so I'm trying to make something that allows a player to have a R6 hitbox while still having an R15 character. To do this: I forced R6, inserted a R16 dummy into ServerStorage and put this script into StarterCharacterScripts (this script isn't complete yet).

wait(1)
local char = script.Parent
local plr = game:GetService("Players"):GetPlayerFromCharacter(char)
local uid = plr.UserId
local charinfo = game:GetService("Players"):GetCharacterAppearanceInfoAsync(uid)
local avatartype = charinfo.playerAvatarType


if avatartype == "R15" then
	local humdesc = game:GetService("Players"):GetHumanoidDescriptionFromUserId(uid)
	humdesc.Parent = game:GetService("ReplicatedStorage").Temp
	-- Makes the character invisible
	plr:ClearCharacterAppearance()
	for i,v in pairs(char:GetChildren()) do
		if v:IsA("Part") then
			-- Removes meshes that are possibly problematic for the next step
			for i2,v2 in pairs(v:GetChildren()) do
				if v2:IsA("BlockMesh") or v2:IsA("SpecialMesh") then
					v2:Destroy()
				end
			end
			-- Makes invisible
			Instance.new("SpecialMesh", v).Scale = Vector3.new(0,0,0)
			-- Hide name
			char.Head.Transparency = 1
		end
	end
	local fchar = game:GetService("ServerStorage").R15:Clone()
	fchar:MakeJoints()
	fchar.Humanoid:ApplyDescription(humdesc) --the error points to here
	fchar.Parent = workspace
end

when I run this, I get the error "DataModel was not available" that points to the line indicated above. I've seen another person with a similar error here, but there are no answers or comments that have helped me.

Thank you so much

also if you need to see the place that I'm doing it in, it's here