GUI Inventory Help?

Your problem is on this line:

if script.Parent.Position == v.Position then

For this to be true, the gui object you're dragging has to be pixel perfect over the one you want to drag it t, assuming they're even in the exact same Frame!

After that, if it doesn't loop on the Frame you're trying to drag it on to dead last, it'll go back to (.05, 0, .05, 0) anyway.

Try this code:

script.Parent.DragStopped:connect(function()
    local target
    for i, v in pairs(script.Parent.Parent.Parent:GetChildren())do
        local sPos = script.Parent.AbsolutePosition
        local vPos = v.AbsolutePosition
        local vSize = v.AbsoluteSize
        if  sPos.X >= vPos.X and sPos.X < vPos.X + vSize.X and sPos.Y >= vPos.Y and sPos.Y < vPos.Y + vSize.Y then
            target = v
            break
        end
    end
    if target then
        script.Parent:TweenPosition(target.Position + UDim2.new(.05, 0, .05, 0), "InOut", "Sine", .5, true)
    else
        script.Parent:TweenPosition(UDim2.new(.05, 0, .05, 0), "InOut", "Sine", .5, true)
            script.Parent.Draggable = true
    end
end)
script.Parent.MouseButton1Click:connect(function()
        script.Parent.Draggable = true
end)