I have purchased a MirPro current loop receiver - transmitter pair. When I tested it, the current loop output (Mir Pro transmitter) is not stable. If I input 4mA on the receiver, it outputs 3.9mA , but every 3-4 second, the current drops to around 1.5mA. It works the same for other current values. What should I do? Please help me, our partners are awaiting for the product.