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?