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. The wiring in the field is a backbone with short branches to each node, so reflections can appear if the board is not designed for that topology. I need a hardware-focused engineer who can dive into the schematic and PCB, pinpoint the weakness, and deliver a proven fix. You’ll have remote access to scope traces and logic-analyzer captures, and I can ship a unit to you if hands-on testing is required. Acceptance criteria • Board communicates error-free with at least four nodes on the branched line at 115 200 bps. • Updated schematic and PCB files (Altium or KiCad) showing the correction, plus a short note explaining the root cause and how it was solved.