I'm trying to make a gui that opens if player is near another player. What is my mistake?

I'm trying to make a first person shooting game with my friends. I need a gui that opens if player press "y" and his cursor is on another player. I'm trying to make a invite to team gui in my game. I wrote this code in a localscript:

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()
local Players = game:GetService("Players")
local workspace_l = game:GetService("Workspace")

local selection = Instance.new("SelectionBox")
selection.Color3 = Color3.fromRGB(255, 0, 0)
selection.Parent = script

mouse.KeyDown:Connect(function(key)
	if key == "Y" or key == "y" then
		local target = workspace:FindPartOnRay(Ray.new(mouse.UnitRay.Origin,mouse.UnitRay.Direction*50000))
		if not target then
			selection.Adornee = nil
		else
			if target.Parent:IsA("Model") then
				local findhumanoid = target.Parent:FindFirstChild ("Humanoid")
				if findhumanoid ~= nil then
					local findplayer = game.Players:FindFirstChild (findhumanoid.Parent.Name)
					if findplayer ~= nil then
						if findplayer ~= player then
							local otherpos = findplayer.Character.HumanoidRootPart.Position
							local frame = script.Parent.InviteMenu.Frame
							local loop = true
							if player.isLeader.Value ~= false then
								if Players[tostring(findplayer)].IsAMemberOf.Value == "Players" then
									repeat
									wait()
										if player:DistanceFromCharacter(Vector3.new(otherpos)) <= 20 then
											if frame.Visible ~= true then
											local userid = findplayer.UserId
											local thumbType = Enum.ThumbnailType.HeadShot
											local thumbSize = Enum.ThumbnailSize.Size100x100
											local content, isReady = Players:GetUserThumbnailAsync(userid, thumbType, thumbSize)
											frame.ImageLabel.Image = content
											frame.ImageLabel.Size = UDim2.new(0, 100, 0, 100)
											frame.target.Value = tostring(findplayer)
											frame.Visible = true
											frame.invite.MouseButton1Click:Connect(function()
											wait()
											loop = false
											end)
										wait()
										end
									else
										loop = false
										frame.Visible = false
										wait()
									end
								until loop == false
								end
								
							end
							
						end
					end
				end
			end
		end
	end
	
end)
	

It works only for some players or some parts of players. What is my mistake? What can I do to make it work?