Stabilize RS485 Board Communication

My in-house RS485 board starts dropping frames and throwing checksum errors as soon as I hook up more than one slave on the bus. With a single device everything is perfect, so I strongly suspect a hardware issue—possibly biasing, termination, or the way the transceiver’s DE/RE lines are handled...

(Budget: ₹600 - ₹1500 INR, Jobs: Circuit Design, Debugging, Electrical Engineering, Electronics, Electronics repair, Embedded Systems, PCB Design and Layout, PCB Layout)